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 A237261 Number of ways to write the n-th odd number in the form of 2^k+p^m*q^h, where p < q are 1 or odd prime numbers, and k, m, h >= 1. 1
 0, 0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 5, 5, 6, 5, 6, 6, 6, 5, 6, 6, 6, 6, 7, 7, 7, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 6, 5, 7, 6 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS Considering 1^m = 1, when p = 1, we always use m = 1. The third zero is a(1622629) = 0. The distribution of the items of this sequence is a bell curve with the mode of 10, which does not likely to grow with n. LINKS Lei Zhou, Table of n, a(n) for n = 1..10000 EXAMPLE 3rd odd number is A005408(3) = 5 = 2^1+1^1*3^1, 1 case; so a(3) = 1. 10th odd number is A005408(10) = 19 = 2^1+1^1*17^1 = 2^2+3^1*5^1 = 2^3+1^1*7^1 = 2^4+1^1*3^1, 4 cases; so a(10) = 4. MAPLE with(numtheory): a:= n-> add(`if`((f-> not 2 in f and 0= 3) && (Length[fi] <= 2), ct++]]; ct, {n, 5, 177, 2}] CROSSREFS Cf. A005408, A000041. Sequence in context: A237720 A075172 A347643 * A004258 A029837 A070939 Adjacent sequences:  A237258 A237259 A237260 * A237262 A237263 A237264 KEYWORD nonn,easy AUTHOR Lei Zhou, Feb 05 2014 STATUS approved

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Last modified June 29 18:25 EDT 2022. Contains 354913 sequences. (Running on oeis4.)