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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
OFFSET
1,1
LINKS
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
Sequence in context: A251103 A065559 A087317 * A015886 A255354 A344349
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Jul 28 2003
EXTENSIONS
More terms from David Wasserman, Mar 09 2005
STATUS
approved