A118431 Numerator of sum of reciprocals of first n 5-simplex numbers A000389.
1, 7, 17, 69, 625, 209, 329, 247, 357, 1250, 341, 1819, 2379, 3059, 19375, 1211, 1496, 3657, 4427, 53125, 12649, 14949, 17549, 10237, 59375, 6851, 7866, 35959, 40919, 231875, 52359, 14726, 16511, 36907, 205625, 91389, 101269
Offset: 1
Examples
a(1) = 1 = numerator of 1/1. a(2) = 7 = numerator of 7/6 = 1/1 + 1/6. a(3) = 17 = numerator of 17/14 = 1/1 + 1/6 + 1/21. a(4) = 69 = numerator of 69/56 = 1/1 + 1/6 + 1/21 + 1/56. a(5) = 55 = numerator of 55/42 = 1/1 + 1/6 + 1/21 + 1/56 + 1/126. a(10) = 1250 = numerator of 1250/1001 = 1/1+ 1/6 + 1/21 + 1/56 + 1/126 + 1/252 + 1/462 + 1/792 + 1/1287 + 1/2002. a(20) = 53125 = numerator of 53125/42504 = 1/1 + 1/6 + 1/21 + 1/56 + 1/126 + 1/252 + 1/462 + 1/792 + 1/1287 + 1/2002 + 1/3003 + 1/4368 + 1/6188 + 1/8568 + 1/11628 + 1/15504 + 1/20349 + 1/26334 + 1/33649 + 1/42504.
Links
- G. C. Greubel, Table of n, a(n) for n = 1..5000
Programs
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Mathematica
Numerator[Accumulate[1/Binomial[Range[5, 50], 5]]] (* G. C. Greubel, Nov 21 2017 *)
Comments