OFFSET
1,2
COMMENTS
Note that primes of the form 4x+3 are not divisors.
EXAMPLE
Irregular triangle:
{1},
{},
{2, 3, 7},
{},
{},
{5, 8, 18, 57, 239},
{4, 13, 21, 38, 47, 268},
{},
{},
{12, 17, 41, 70, 99, 157, 307},
{},
{6, 31, 43, 68, 117, 191, 302, 327, 882, 18543},
{9, 32, 73, 132, 278, 378, 829, 993, 2943}
MATHEMATICA
t = Table[FactorInteger[n^2 + 1][[-1, 1]], {n, 10^5}]; Table[Flatten[Position[t, Prime[n]]], {n, 13}]
CROSSREFS
KEYWORD
nonn,tabf
AUTHOR
T. D. Noe, Apr 03 2013
STATUS
approved