login
A269841
Integers n such that A000330(n) is the sum of 2 nonzero squares.
0
2, 12, 24, 25, 26, 48, 50, 60, 73, 74, 96, 97, 120, 121, 122, 145, 146, 156, 169, 194, 204, 240, 242, 289, 312, 337, 338, 348, 361, 362, 410, 432, 457, 480, 492, 529, 554, 578, 600, 624, 673, 722, 732, 768, 793, 842, 865, 866, 876, 960, 961, 985
OFFSET
1,1
COMMENTS
Corresponding square pyramidal numbers are 5, 650, 4900, 5525, 6201, 38024, 42925, 73810, 132349, 137825, 299536, 308945, 583220, 597861, 612745, 1026745, ...
EXAMPLE
12 is a term because A000330(12) = 1^2 + 2^2 + ... + 11^2 + 12^2 = 650 = 5^2 + 25^2.
MATHEMATICA
Select[Range@ 1000, SquaresR[2, Binomial[# + 2, 3] + Binomial[# + 1, 3]] > 0 &] (* Michael De Vlieger, Mar 06 2016 *)
PROG
(PARI) isA000404(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(isA000404(n*(n+1)*(2*n+1)/6), print1(n, ", ")));
CROSSREFS
Sequence in context: A365500 A117301 A141079 * A144551 A174457 A353011
KEYWORD
nonn
AUTHOR
Altug Alkan, Mar 06 2016
STATUS
approved