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A130200
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Evil triangular numbers.
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1
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3, 6, 10, 15, 36, 45, 66, 78, 105, 120, 136, 153, 190, 210, 231, 300, 325, 378, 435, 528, 561, 630, 703, 741, 780, 903, 946, 990, 1035, 1128, 1176, 1275, 1326, 1596, 1711, 1830, 1953, 2016, 2080, 2145, 2278, 2415, 2556, 2628, 2701, 2775, 2926, 3081, 3321
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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FORMULA
| a(n) = A130199(n)/2. Multiplying by 2 doesn't change evilness. Hence evil oblong numbers are twice evil triangular numbers.
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EXAMPLE
| 3 belongs to the sequence because the binary expansion of 3 is 11 - contains an even number of ones.
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MATHEMATICA
| Select[Table[n(n + 1)/2, {n, 100}], EvenQ[Plus @@ IntegerDigits[ #, 2]] &]
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CROSSREFS
| Cf. This sequence is the intersection of evil numbers (A001969) and triangular numbers (A000217).
Sequence in context: A024674 A026104 A058576 * A202269 A151375 A153453
Adjacent sequences: A130197 A130198 A130199 * A130201 A130202 A130203
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KEYWORD
| nonn
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AUTHOR
| Tanya Khovanova (tanyakh(AT)yahoo.com), May 16 2007
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