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A231118
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Numbers n such that n*91^k is palindromic for k=0,...,4
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1
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14641, 147741, 1478741, 14788741, 146424641, 147767741, 147888741, 1464114641, 1476226741, 1477557741, 1478778741, 1478888741, 1489779841, 14641014641, 14762026741, 14774247741, 14775457741, 14787678741, 14788888741, 14883038841, 14895259841, 14896469841
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OFFSET
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1,1
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COMMENTS
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Necessarily a subsequence of A002113.
It is an open question whether there exists a,r>1 such that a*r^k is palindromic for k=0,...,5.
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LINKS
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PROG
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(PARI) ispal(n)=my(v=digits(n)); for(i=1, #v\2, if(v[i]!=v[#v+1-i], return(0))); 1
has(n)=for(k=1, 4, if(!ispal(n*=91), return(0))); 1
u=List(); for(n=1, 10^5-1, for(m=-1, 9, v=digits(n); v=if(m<0, concat(v, Vecrev(v)), concat(concat(v, m), Vecrev(v))); N=subst(Pol(v), x, 10); if(has(N), listput(u, N)))); Set(u) \\ Charles R Greathouse IV, Nov 04 2013
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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