login
A250004
Numbers representable as x^y + x*y, where x>1, y>1 are integers (without multiplicity).
1
8, 14, 15, 24, 35, 36, 42, 48, 63, 76, 80, 93, 99, 120, 140, 142, 143, 168, 195, 224, 234, 255, 258, 272, 288, 323, 360, 364, 399, 440, 483, 528, 530, 536, 575, 624, 645, 675, 728, 747, 756, 783, 840, 899, 960, 1023, 1030, 1044, 1088, 1155, 1224, 1295, 1320, 1364, 1368
OFFSET
1,1
COMMENTS
The sequence of numbers representable as x^y + x*y in two or more ways begins: 24, 76, 272, 1044, 2208, 4120, 16412. Example: 2208 = 46^2 + 46*2 = 3^7 + 3*7.
The subsequence of squares begins: 36, 1764.
EXAMPLE
a(2) = 14 = 2^3 + 2*3.
a(3) = 15 = 3^2 + 3*2.
a(22) = 255 = 15^2 + 15*2.
PROG
(PARI) isok(n) = {for (p=2, floor(log(n)/log(2)), for (k=2, sqrtnint(n, p), if (n == k^p + p*k, return (1)); ); ); return (0); } \\ Michel Marcus, Jan 16 2015
CROSSREFS
Cf. A253775.
Cf. A024036 is a subsequence, except first 2 terms.
Sequence in context: A376519 A082772 A103338 * A114456 A230422 A050681
KEYWORD
nonn
AUTHOR
Alex Ratushnyak, Jan 14 2015
STATUS
approved