Added Natural numbers and Isomorphic sets
Added Natural numbers and Isomorphic sets

kaushik94/sympy,pandeyadarsh/sympy,liangjiaxing/sympy,Mitchkoens/sympy,garvitr/sympy,asm666/sympy,postvakje/sympy,shipci/sympy,yashsharan/sympy,Arafatk/sympy,moble/sympy,oliverlee/sympy,wanglongqi/sympy,Sumith1896/sympy,kevalds51/sympy,cccfran/sympy,mcdaniel67/sympy,Titan-C/sympy,MridulS/sympy,abhiii5459/sympy,kevalds51/sympy,MechCoder/sympy,farhaanbukhsh/sympy,farhaanbukhsh/sympy,lindsayad/sympy,pandeyadarsh/sympy,vipulroxx/sympy,jerli/sympy,abloomston/sympy,cswiercz/sympy,ga7g08/sympy,debugger22/sympy,mafiya69/sympy,bukzor/sympy,abhiii5459/sympy,mcdaniel67/sympy,wyom/sympy,madan96/sympy,pandeyadarsh/sympy,shipci/sympy,kumarkrishna/sympy,debugger22/sympy,AunShiLord/sympy,hargup/sympy,debugger22/sympy,jamesblunt/sympy,AunShiLord/sympy,vipulroxx/sympy,jbbskinny/sympy,sunny94/temp,Shaswat27/sympy,garvitr/sympy,jaimahajan1997/sympy,pbrady/sympy,ChristinaZografou/sympy,jaimahajan1997/sympy,Davidjohnwilson/sympy,AkademieOlympia/sympy,Titan-C/sympy,cccfran/sympy,Sumith1896/sympy,Arafatk/sympy,saurabhjn76/sympy,VaibhavAgarwalVA/sympy,sahilshekhawat/sympy,sahilshekhawat/sympy,bukzor/sympy,shipci/sympy,sampadsaha5/sympy,atsao72/sympy,hrashk/sympy,grevutiu-gabriel/sympy,cswiercz/sympy,iamutkarshtiwari/sympy,lidavidm/sympy,Davidjohnwilson/sympy,moble/sympy,garvitr/sympy,emon10005/sympy,abhiii5459/sympy,sahilshekhawat/sympy,Mitchkoens/sympy,rahuldan/sympy,ahhda/sympy,ChristinaZografou/sympy,hrashk/sympy,jbbskinny/sympy,jerli/sympy,drufat/sympy,aktech/sympy,meghana1995/sympy,drufat/sympy,lindsayad/sympy,amitjamadagni/sympy,cswiercz/sympy,Mitchkoens/sympy,MridulS/sympy,maniteja123/sympy,ga7g08/sympy,Gadal/sympy,madan96/sympy,shikil/sympy,Designist/sympy,mcdaniel67/sympy,toolforger/sympy,jaimahajan1997/sympy,oliverlee/sympy,skidzo/sympy,wanglongqi/sympy,Vishluck/sympy,Shaswat27/sympy,meghana1995/sympy,Designist/sympy,AkademieOlympia/sympy,AkademieOlympia/sympy,wyom/sympy,rahuldan/sympy,shikil/sympy,Arafatk/sympy,asm666/sympy,toolforger/sympy,maniteja123/sympy,hargup/sympy,Sumith1896/sympy,yashsharan/sympy,ahhda/sympy,bukzor/sympy,cccfran/sympy,ga7g08/sympy,Designist/sympy,saurabhjn76/sympy,sahmed95/sympy,yukoba/sympy,MechCoder/sympy,Gadal/sympy,atreyv/sympy,Shaswat27/sympy,pbrady/sympy,AunShiLord/sympy,maniteja123/sympy,toolforger/sympy,kmacinnis/sympy,kumarkrishna/sympy,MridulS/sympy,atsao72/sympy,asm666/sympy,iamutkarshtiwari/sympy,Gadal/sympy,flacjacket/sympy,Curious72/sympy,souravsingh/sympy,kmacinnis/sympy,yashsharan/sympy,farhaanbukhsh/sympy,rahuldan/sympy,kaushik94/sympy,sahmed95/sympy,Vishluck/sympy,dqnykamp/sympy,hrashk/sympy,vipulroxx/sympy,atreyv/sympy,postvakje/sympy,chaffra/sympy,souravsingh/sympy,aktech/sympy,mafiya69/sympy,skidzo/sympy,Curious72/sympy,moble/sympy,atreyv/sympy,amitjamadagni/sympy,shikil/sympy,madan96/sympy,jbbskinny/sympy,meghana1995/sympy,lidavidm/sympy,skirpichev/omg,sunny94/temp,atsao72/sympy,kmacinnis/sympy,yukoba/sympy,VaibhavAgarwalVA/sympy,grevutiu-gabriel/sympy,sahmed95/sympy,lidavidm/sympy,kaushik94/sympy,beni55/sympy,wyom/sympy,Vishluck/sympy,hargup/sympy,beni55/sympy,kevalds51/sympy,kumarkrishna/sympy,MechCoder/sympy,beni55/sympy,lindsayad/sympy,jerli/sympy,chaffra/sympy,Titan-C/sympy,emon10005/sympy,yukoba/sympy,dqnykamp/sympy,dqnykamp/sympy,aktech/sympy,abloomston/sympy,abloomston/sympy,pbrady/sympy,grevutiu-gabriel/sympy,mafiya69/sympy,jamesblunt/sympy,postvakje/sympy,wanglongqi/sympy,drufat/sympy,liangjiaxing/sympy,sampadsaha5/sympy,diofant/diofant,jamesblunt/sympy,Curious72/sympy,iamutkarshtiwari/sympy,VaibhavAgarwalVA/sympy,sampadsaha5/sympy,saurabhjn76/sympy,kaichogami/sympy,chaffra/sympy,Davidjohnwilson/sympy,srjoglekar246/sympy,kaichogami/sympy,oliverlee/sympy,sunny94/temp,skidzo/sympy,liangjiaxing/sympy,souravsingh/sympy,emon10005/sympy,ahhda/sympy,ChristinaZografou/sympy,kaichogami/sympy