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A264890 Integers n such that n! + 1 is the sum of 2 nonzero squares. 0
0, 1, 4, 8, 11, 12, 17, 25, 26, 27, 28, 29, 37, 38, 41, 45, 48, 54, 60, 67, 71, 73, 75, 77 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..24.

EXAMPLE

a(3) = 4 because 4! + 1 = 4^2 + 3^2.

MATHEMATICA

Flatten@ Position[Map[Length, Map[Map[Length, PowersRepresentations[#, 2, 2] &@(#! + 1) /. 0 -> Nothing] &, Range[0, 48]] /. 1 -> Nothing], n_ /; n > 0] - 1 (* Michael De Vlieger, Nov 28 2015 *)

PROG

(PARI) is(n) = { for( i=1, #n=factor(n)~%4, n[1, i]==3 && n[2, i]%2 && return); n && ( vecmin(n[1, ])==1 || (n[1, 1]==2 && n[2, 1]%2)) }

for(n=0, 1e3, if(is(n!+1), print1(n, ", ")))

CROSSREFS

Cf. A000404, A038507.

Sequence in context: A288150 A311019 A068798 * A272299 A282144 A147515

Adjacent sequences:  A264887 A264888 A264889 * A264891 A264892 A264893

KEYWORD

nonn,more

AUTHOR

Altug Alkan, Nov 27 2015

STATUS

approved

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Last modified May 24 06:53 EDT 2019. Contains 323529 sequences. (Running on oeis4.)