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A130202 Odious triangular numbers. 2
1, 21, 28, 55, 91, 171, 253, 276, 351, 406, 465, 496, 595, 666, 820, 861, 1081, 1225, 1378, 1431, 1485, 1540, 1653, 1770, 1891, 2211, 2346, 2485, 2850, 3003, 3160, 3240, 3403, 3655, 3916, 4186, 4371, 4560, 4753, 4950 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Harvey P. Dale, Table of n, a(n) for n = 0..1000

FORMULA

a(n) = A130201(n)/2. Multiplication by 2 preserves odiousness, hence this sequence is odious oblong numbers divided by 2.

MATHEMATICA

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

Select[Accumulate[Range[100]], OddQ[DigitCount[#, 2, 1]]&] (* Harvey P. Dale, Dec 04 2016 *)

CROSSREFS

Cf. This sequence is the intersection of odious (A000069) and triangular (A000217) numbers.

Sequence in context: A048012 A254368 A276674 * A162692 A048067 A212192

Adjacent sequences:  A130199 A130200 A130201 * A130203 A130204 A130205

KEYWORD

nonn

AUTHOR

Tanya Khovanova, May 16 2007

STATUS

approved

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Last modified March 27 01:05 EDT 2017. Contains 284141 sequences.