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Search: id:A075721
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| A075721 |
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a(n+1) = least k with sum of prime factors (with repetition) = a(n)+1. |
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+0
1
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| 2, 3, 4, 5, 8, 14, 26, 92, 356, 1412, 5636, 185559, 556671, 21152738, 42305474, 2919075981, 14595379885, 102167659153, 3882371047054, 361060507372953, 16969843846526629, 1561225633880447476, 6244902535521789892
(list; graph; listen)
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OFFSET
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0,1
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EXAMPLE
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92 is a term because it is the smallest number such that its sum of prime factors is equal to the previous term + 1; 92 = 2^2*23 and 2+2+23 = 26+1.
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PROGRAM
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(PARI) v = vector(200); count = 0; m = 2; print1("2 3 4 5 8 "); n = 8; while (count < 199, f = factor(m); s = sum(i = 1, matsize(f)[1], f[i, 1]*f[i, 2]); if (s <= 200 && v[s] == 0, count++; v[s] = m); m++); for (i = 1, 20, p = precprime(n + 1); if (p == n + 1, n++; print1(n, " "), b = v[n + 1 - p]; c = p; while (b > n + 1 - p, p = precprime(p - 1); m = v[n + 1 - p]; if (m < b, b = m; c = p)); n = b*c; print1(n, " "))); (Wasserman)
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CROSSREFS
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Sequence in context: A162900 A140294 A108014 this_sequence A112479 A081711 A055638
Adjacent sequences: A075718 A075719 A075720 this_sequence A075722 A075723 A075724
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KEYWORD
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nonn
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AUTHOR
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Jason Earls (zevi_35711(AT)yahoo.com), Oct 03 2002
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EXTENSIONS
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More terms from David Wasserman (dwasserm(AT)earthlink.net), Jan 23 2005
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