A335031 -id:A335031

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A334919

Numbers of the form i + j + 3*i*j for i,j >= 1 together with numbers of the form -i - j + 3*i*j for i,j >= 2.

+10
2

5, 8, 9, 13, 16, 17, 18, 21, 23, 25, 28, 29, 30, 33, 37, 38, 40, 41, 43, 44, 45, 48, 49, 51, 53, 56, 57, 58, 61, 62, 63, 65, 68, 69, 72, 73, 77, 78, 79, 81, 82, 83, 84, 85, 86, 88, 89, 93, 95, 96, 97, 98, 100, 101, 103, 105, 106, 107, 108, 109, 113, 114, 117

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..63.

EXAMPLE

5 is a term because 5 = 1+1+3*1*1.

8 is a term because 8 = -2-2+3*2*2.

16 is a term because 16 = 2+2+3*2*2.

PROG

(Magma) [m:m in [1..101]|exists(a){i:i in [1..m-1]|IsIntegral((m-i)/(1+3*i))} or exists(b){j:j in [2..m-1]|IsIntegral((m+j)/(-1+3*j)) and (m+j)/(-1+3*j) ge 2}]; // Marius A. Burtea, Jun 04 2020

CROSSREFS

Complement of A335031.

KEYWORD

nonn

AUTHOR

Davide Rotondo, May 16 2020

STATUS

approved

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