A091462 a(n) is the smallest j such that 1/3 + 1/6 + 1/9 + ... + 1/j exceeds n.

3, 33, 681, 13650, 274140, 5506263, 110596236, 2221384803, 44617706493, 896170591203, 18000067499079, 361541020372644, 7261745513941683, 145856057647068072, 2929597231340774769, 58842533360163495285, 1181883876459465987195, 23738772239546776075803, 476805986328559173414774

Offset: 0

Author

Robert G. Wilson v, Jan 12 2004

Keywords

• nonn

Crossrefs

Cf. A002387, A056053, A056054, A091463, A091464.

Programs

Mathematica

s = 0; k = 3; Do[ While[s = N[s + 1/k, 24]; s <= n, k += 3]; Print[k]; k += 3, {n, 1, 12}]

Formula

a(n) = 3*A002387(3n).

The next term is approximately the previous term * e^3.

Extensions

a(0) prepended and more terms added by Max Alekseyev, Sep 01 2023