

A130199


Evil oblong (pronic) numbers.


2



0, 6, 12, 20, 30, 72, 90, 132, 156, 210, 240, 272, 306, 380, 420, 462, 600, 650, 756, 870, 1056, 1122, 1260, 1406, 1482, 1560, 1806, 1892, 1980, 2070, 2256, 2352, 2550, 2652, 3192, 3422, 3660, 3906, 4032, 4160, 4290, 4556, 4830, 5112, 5256, 5402, 5550, 5852
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OFFSET

1,2


LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000


FORMULA

a(n) = 2*A130200(n). Multiplying by 2 doesn't change evilness. Hence evil oblong numbers are twice evil triangular numbers.


EXAMPLE

6 belongs to the sequence because binary expansion of 6 is 110  contains an even number of ones.


MATHEMATICA

Select[Table[n(n + 1), {n, 0, 100}], EvenQ[Plus @@ IntegerDigits[ #, 2]] &]


CROSSREFS

Cf. This sequence is the intersection of evil numbers (A001969) and oblong numbers (A002378).
Sequence in context: A056930 A326378 A064971 * A295904 A309836 A117343
Adjacent sequences: A130196 A130197 A130198 * A130200 A130201 A130202


KEYWORD

nonn


AUTHOR

Tanya Khovanova, May 16 2007


EXTENSIONS

a(1) = 0 inserted and offset corrected by Amiram Eldar, Dec 09 2019


STATUS

approved



