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

1,1

Links

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

Formula

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

Example

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

Mathematica

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

Crossrefs

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

Sequence in context: A138667 A290462 A355790 * A262743 A176819 A114407

Adjacent sequences: A240524 A240525 A240526 * A240528 A240529 A240530

Keyword

nonn

Author

Vincenzo Librandi, Apr 07 2014

Status

approved