OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..500
EXAMPLE
447 is a term because the distinct prime divisors of 447^2 + 1 are 2, 5, 13, 29, 53 and their sum, 2 + 5 + 13 + 29 + 53 = 102, equals 2*(53 - 2).
MATHEMATICA
Select[Range[1800000], Plus@@(pl=First/@FactorInteger[#^2+1])/2==pl[[-1]]-pl[[1]]&]
spddQ[n_]:=Module[{fi=FactorInteger[n^2+1][[All, 1]]}, Total[fi] == 2*(Last[ fi]-First[fi])]; Select[Range[176*10^4], spddQ] (* Harvey P. Dale, Jan 12 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Nov 13 2011
STATUS
approved