OFFSET
1,1
COMMENTS
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
EXAMPLE
MAPLE
with(numtheory):T:=array(1..100): for n from 1 to 100 do:x:=factorset(n^2+1):n1:=nops(x): T[n] := x[1]:od:for a from 1 to 80 do:p:=T[a]:ii:=0:for k from 1 to 50000 while(ii=0) do: z:=factorset((a+k)^2+1): n2:=nops(z):if z[1]=p then printf(`%d, `, k):ii:=1:else fi:od:od:
MATHEMATICA
sspf[n_]:=Module[{c=FactorInteger[1+n^2][[1, 1]], k=1}, While[ FactorInteger[ 1+ (n+k)^2][[1, 1]]!=c, k++]; k]; Array[sspf, 80] (* Harvey P. Dale, Oct 12 2012 *)
PROG
(PARI)
A020639(n) = if(1==n, n, factor(n)[1, 1]);
A217448(n) = { my(spf=A020639(1+(n^2)), x); for(k=1, oo, x=1+((n+k)^2); if(!(x%spf) && A020639(x)==spf, return(k))); }; \\ Antti Karttunen, May 24 2021
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Michel Lagneau, Oct 03 2012
STATUS
approved