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Search: id:A086489
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| A086489 |
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Smallest k such that k and k + n have the same prime signature. |
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+0
4
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| 2, 3, 2, 3, 2, 5, 14, 3, 2, 3, 2, 5, 21, 3, 2, 3, 2, 5, 8, 3, 2, 7, 10, 5, 10, 3, 2, 3, 2, 7, 15, 5, 6, 3, 2, 5, 14, 3, 2, 3, 2, 5, 14, 3, 2, 7, 10, 5, 6, 3, 2, 6, 21, 5, 10, 3, 2, 3, 2, 7, 21, 5, 6, 3, 2, 5, 10, 3, 2, 3, 2, 7, 14, 5, 10, 3, 2, 5, 6, 3, 2, 7, 10, 5, 6, 3, 2, 6, 6, 7, 15, 5, 22, 3, 2, 5, 14
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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a(7) = 14 as 14 and 14+7 = 21 have the same prime signature p*q.
a(13) = 21 as 21 is the smallest number such that 21 +13 = 34 and 21 both have the same prime signature p*q.
a(19) = 8 as 8 +19 = 27 = 3^3,8 = 2^3 both have the prime signature p^3.
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PROGRAM
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(PARI) ps(n) = local(f); f = factor(n); vecsort(f[, 2]); a(n) = local(P, m, v); P = vector(n, i, ps(i)); m = 1; while (1, for (i = 1, n, v = ps(m*n + i); if (v == P[i], return((m - 1)*n + i), P[i] = v)); m++); (Wasserman)
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CROSSREFS
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Cf. A085072, A085876.
Sequence in context: A120223 A065559 A087317 this_sequence A015886 A108656 A164962
Adjacent sequences: A086486 A086487 A086488 this_sequence A086490 A086491 A086492
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Jul 28 2003
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EXTENSIONS
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More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Mar 09 2005
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