The On-Line Encyclopedia of Integer Sequences (OEIS)

A126253 revision #10

A126253

a(n) = n-th integer from among those positive integers which are each coprime to exactly one prime dividing n.

3, 4, 7, 6, 10, 8, 15, 13, 18, 12, 22, 14, 26, 36, 31, 18, 34, 20, 38, 54, 42, 24, 46, 31, 50, 40, 54, 30, 130, 32, 63, 88, 66, 120, 70, 38, 74, 105, 78, 42, 192, 44, 86, 111, 90, 48, 94, 57, 98, 141, 102, 54, 106, 210, 110, 159, 114, 60, 255, 62, 122, 162

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OFFSET

2,1

LINKS

Table of n, a(n) for n=2..63.

EXAMPLE

The positive integers which are each coprime to exactly one prime dividing 12 form the sequence: 2,3,4,8,9,10,14,15,16,20,21,22,26,27,28... The 12th of these is 22; so a(12) = 22.

PROG

(PARI) a(n) = {ok = 0; nb = 0; i = 1; pf = factor(n)[, 1]; while(! ok, if (sum(j=1, #pf, gcd(i, pf[j]) == 1) == 1, nb++); if (nb == n, ok = 1, i++); ); i; } \\ Michel Marcus, Feb 10 2014

CROSSREFS

Cf. A125704, A128487.

Sequence in context: A087030 A175187 A332993 * A057032 A347529 A279388

Adjacent sequences: A126250 A126251 A126252 * A126254 A126255 A126256

KEYWORD

nonn

AUTHOR

Leroy Quet, Mar 08 2007

EXTENSIONS

Offset corrected and more terms from Michel Marcus, Feb 10 2014

STATUS

approved