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A319293
Numbers of the form 27^i*(9*j +- 1).
1
1, 8, 10, 17, 19, 26, 27, 28, 35, 37, 44, 46, 53, 55, 62, 64, 71, 73, 80, 82, 89, 91, 98, 100, 107, 109, 116, 118, 125, 127, 134, 136, 143, 145, 152, 154, 161, 163, 170, 172, 179, 181, 188, 190, 197, 199, 206, 208, 215, 216, 217, 224, 226, 233, 235, 242, 244
OFFSET
1,2
COMMENTS
{+-a(n)} gives all nonzero cubes modulo all powers of 3, that is, cubes over 3-adic integers. So this sequence is closed under multiplication.
LINKS
Jianing Song, Table of n, a(n) for n = 1..9231 (all terms <= 40000)
FORMULA
a(n) = 13*n/3 + O(log(n)).
PROG
(PARI) isA319293(n)= n\27^valuation(n, 27)%9==1||n\27^valuation(n, 27)%9==8
CROSSREFS
A056020 is a proper subsequence.
Perfect powers over 3-adic integers:
Squares: positive: A055047; negative: A055048 (negated);
Cubes: this sequence.
Sequence in context: A155966 A228072 A038209 * A061908 A056020 A049510
KEYWORD
nonn
AUTHOR
Jianing Song, Sep 16 2018
STATUS
approved