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A240528
Indices of 8-almost prime triangular numbers.
2
63, 80, 128, 256, 287, 288, 319, 320, 324, 383, 399, 440, 447, 480, 495, 539, 560, 567, 576, 608, 640, 648, 671, 675, 703, 720, 729, 799, 831, 863, 927, 935, 972, 975, 1000, 1007, 1055, 1056, 1071, 1079, 1080, 1104, 1119, 1120, 1160, 1175, 1183, 1184
OFFSET
1,1
LINKS
Muniru A Asiru, Table of n, a(n) for n = 1..10000 (first 1000 terms from Vincenzo Librandi)
FORMULA
{ m : A069904(m) = 8 }. - Alois P. Heinz, Aug 05 2019
EXAMPLE
a(1) = 63 because A000217(63) = 63*(63+1)/2 = 2016 = 2^5 * 3^2 * 7 is an 8-almost prime.
MATHEMATICA
Flatten[Position[Accumulate[Range[1500]], _?(PrimeOmega[#]== 8 &)]]
PROG
(GAP) F:=List([1..1200], n->Length(Factors(n*(n+1)/2)));; a:=Filtered([1..Length(F)], i->F[i]=8); # Muniru A Asiru, Dec 22 2018
(Magma) [n: n in [2..1200] | &+[d[2]: d in Factorization((n*(n+1)))] eq 9]; // Vincenzo Librandi, Dec 22 2018
CROSSREFS
Cf. A046310 (8-almost primes).
Sequence in context: A238088 A350960 A046049 * A320066 A372557 A372558
KEYWORD
nonn
AUTHOR
Vincenzo Librandi, Apr 07 2014
STATUS
approved