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 A295012 a(n) = sigma(12n - 1)/12, where sigma = sum of divisors (A000203). 1
 1, 2, 4, 4, 5, 6, 7, 10, 9, 12, 11, 14, 16, 14, 15, 16, 20, 22, 19, 20, 21, 22, 31, 28, 28, 26, 30, 34, 29, 30, 36, 32, 40, 38, 35, 36, 37, 56, 39, 40, 41, 42, 52, 48, 57, 50, 47, 62, 49, 50, 56, 60, 64, 54, 55, 62, 57, 70, 68, 60, 66, 62, 76, 70, 70, 76 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Robert G. Wilson v observes in A280098 that {1, 3, 4, 6, 8, 12, 24} seem to be the only positive integers k such that sigma(kn-1)/k is an integer for all n > 0. LINKS Muniru A Asiru, Table of n, a(n) for n = 1..100000 MAPLE with(numtheory): seq(sigma(12*n-1)/12, n=1..10^3); # Muniru A Asiru, Dec 28 2017 MATHEMATICA Array[DivisorSigma[1, 12 # - 1]/12 &, 66] (* Michael De Vlieger, Dec 08 2017 *) PROG (PARI) vector(90, n, sigma(12*n-1)/12) (GAP) sequence := List([1..10^5], n-> Sigma(12 *n-1)/12); # Muniru A Asiru, Dec 28 2017 CROSSREFS Cf. A280098 (analog for k = 24), A097723 (analog for k = 4), A033686 (analog for k = 3), A000203 (sigma, also the  analog for k = 1). The analog for k = 8 is A258835, up to the offset. The analog for k = 6 is A098098 (up to the offset), a signed variant of this and the preceding one is A258831. Sequence in context: A214880 A071193 A071192 * A308629 A100921 A140201 Adjacent sequences:  A295009 A295010 A295011 * A295013 A295014 A295015 KEYWORD nonn AUTHOR M. F. Hasler, Dec 08 2017 STATUS approved

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Last modified February 20 07:41 EST 2020. Contains 332069 sequences. (Running on oeis4.)