A380509 Numbers of the form i+j+4ij for i,j >= 1 together with numbers of the form -i-j+4ij for i,j >= 2.

6, 11, 12, 16, 19, 20, 21, 26, 29, 30, 31, 33, 36, 38, 40, 41, 42, 46, 47, 51, 52, 54, 55, 56, 61, 63, 65, 66, 68, 71, 72, 74, 75, 76, 81, 82, 83, 85, 86, 89, 90, 91, 92, 94, 96, 101, 103, 106, 107, 109, 110, 111, 116, 117, 118, 119, 120, 121, 123, 124, 126, 128, 129, 131, 132, 133

Offset

1,1

Links

Table of n, a(n) for n=1..66.

Example

1+1+4*1*1 = 6; -2-2+4*2*2 = 12.

Maple

L := 150: S := {}:
for i to L do for j to L do
if 4*i*j + i + j <= L then S := `union`(S, {4*i*j+i+j}, {4*i*j+3*i+3*j+2}) fi;
od; od;
S; # Peter Bala, Jan 30 2025

Crossrefs

Cf. A054520, A380140, A380572 (complement), A380549, A380550.

Sequence in context: A152089 A212773 A389683 * A230996 A219553 A015870

Adjacent sequences: A380506 A380507 A380508 * A380510 A380511 A380512

Keyword

nonn

Author

Davide Rotondo, Jan 26 2025

Extensions

More terms from Stefano Spezia, Jan 26 2025

Missing terms 111, 121 and 126 added by Peter Bala, Jan 30 2025

Status

approved