OFFSET
1,1
LINKS
Charles R Greathouse IV and Zak Seidov, Table of n, a(n) for n = 1..500 (1..100 from Levin)
EXAMPLE
1560 is in the sequence because the sum of the prime distinct divisors of 1560^2+1 is 17+37+53+73=180 and 1560^2 /180=13520.
MAPLE
with(numtheory):for k from 1 to 120000 do: y:=factorset(k^2+1): s:=sum(y[i], i=1..nops(y)):if irem(k^2, s)=0 then printf(`%d, `, k):else fi:od:
MATHEMATICA
c=0; s={}; Do[If[PowerMod[n, 2, Plus@@First/@FactorInteger[n^2+1]]==0, AppendTo[s, n]; c++; If[c==100, Break[]]], {n, 2*10^6}]; s (* Zak Seidov, Oct 14 2011 *)
PROG
(PARI) is(n)=my(f=factor(n^2+1)[, 1]); n^2%sum(i=1, #f, f[i])==0 \\ Charles R Greathouse IV, Oct 25 2011
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Sep 29 2011
STATUS
approved