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 A086489 Smallest k such that k and k + n have the same prime signature. 4
 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; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Alois P. Heinz, Table of n, a(n) for n = 1..20000 EXAMPLE 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. PROG (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++); \\ David Wasserman, Mar 09 2005 CROSSREFS Cf. A085072, A085876. Sequence in context: A251103 A065559 A087317 * A015886 A255354 A318620 Adjacent sequences:  A086486 A086487 A086488 * A086490 A086491 A086492 KEYWORD nonn AUTHOR Amarnath Murthy, Jul 28 2003 EXTENSIONS More terms from David Wasserman, Mar 09 2005 STATUS approved

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Last modified August 20 01:14 EDT 2019. Contains 326136 sequences. (Running on oeis4.)