A240527 Indices of 7-almost prime triangular numbers.

64, 95, 127, 135, 143, 144, 159, 160, 175, 191, 192, 207, 215, 216, 242, 243, 272, 279, 296, 323, 335, 350, 360, 368, 375, 404, 405, 415, 416, 431, 432, 448, 455, 459, 464, 479, 485, 504, 527, 528, 543, 544, 559, 584, 594, 615, 620, 623, 647, 656, 672, 719

Offset: 1

Author

Vincenzo Librandi, Apr 07 2014

Keywords

• nonn

Examples

			a(1) = 64 because A000217(64) = 64*(64+1)/2 = 2080 = 2^5 * 5 * 13 is a 7-almost prime.
		

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000217, A069904, A108815, A114435, A114436, A114437, A164977.

Programs

Mathematica

Flatten[Position[Accumulate[Range[800]],_?(PrimeOmega[#]==7&)]]

Formula

{ m : A069904(m) = 7 }. - Alois P. Heinz, Aug 05 2019