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A139116
a(n) = p*(p-1)/2, where p is A000043(n).
6
1, 3, 10, 21, 78, 136, 171, 465, 1830, 3916, 5671, 8001, 135460, 183921, 817281, 2425503, 2600340, 5172936, 9041878, 9779253, 46933516, 49406770, 62860078, 198732016, 235455850, 269317236, 989969256, 3718884403, 6105401253, 8718403176, 23347552095, 286402257541
OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..48 (terms 1..47 from Harvey P. Dale)
FORMULA
a(n) = A000043(n)*(A000043(n)-1)/2.
MATHEMATICA
(#(#-1))/2&/@MersennePrimeExponent[Range[47]] (* Harvey P. Dale, Aug 13 2021 *)
KEYWORD
nonn
AUTHOR
Omar E. Pol, May 10 2008
EXTENSIONS
a(24)-a(32) from Harvey P. Dale, Aug 13 2021
STATUS
approved