

A125504


Smallest number k such that the numerator of alternating generalized harmonic number H'(k,n) = Sum[ (1)^(i+1) * 1/i^n, {i,1,k} ] is a prime.


0



3, 2, 2, 3, 2, 19, 2, 146, 87, 3, 16, 3, 2, 249, 15, 87, 2, 699, 2
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OFFSET

1,1


COMMENTS

a(n) = 2 for n in A000043.
a(n) = 3 for n in {1,4,10,12,24,27,39,...}.
a(n) = 5 for n in {26,76,132,205,238,...}.
a(n) = 9 for n in {100,200,...}.
a(n) = 15 for n in {15,33,65,...}.
a(21) = 18. a(22) = 13. a(41) = 6. a(72) = 11. a(173) = 8.
a(20) > 2100 [From Max Alekseyev, Jul 07 2009]


LINKS

Table of n, a(n) for n=1..19.
Eric Weisstein, Link to a section of The World of Mathematics. Harmonic Number.


CROSSREFS

Cf. A058313, A119682, A120296, A001008, A000043.
Sequence in context: A049234 A299351 A294299 * A243929 A075392 A069901
Adjacent sequences: A125501 A125502 A125503 * A125505 A125506 A125507


KEYWORD

hard,more,nonn


AUTHOR

Alexander Adamchuk, Dec 28 2006, Jan 31 2007


EXTENSIONS

More terms from Max Alekseyev, Jul 07 2009


STATUS

approved



