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A139117
Triangular numbers (A000217) with indices A000043.
1
3, 6, 15, 28, 91, 153, 190, 496, 1891, 4005, 5778, 8128, 135981, 184528, 818560, 2427706, 2602621, 5176153, 9046131, 9783676, 46943205, 49416711, 62871291, 198751953, 235477551, 269340445, 990013753, 3718970646, 6105511756, 8718535225, 23347768186, 286403014380
OFFSET
1,1
LINKS
FORMULA
a(n) = A000217(A000043(n)).
EXAMPLE
a(4) = 28 because A000043(4) = 7 and the 7th triangular number A000217(7) is 28.
MATHEMATICA
Map[#*(#+1)/2 &, MersennePrimeExponent[Range[48]]] (* Amiram Eldar, Oct 21 2024 *)
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
Omar E. Pol, May 08 2008
STATUS
approved