The On-Line Encyclopedia of Integer Sequences (OEIS)

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A126253

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

#10 by Bruno Berselli at Mon Feb 10 03:29:21 EST 2014

STATUS

reviewed

approved

#9 by Joerg Arndt at Mon Feb 10 02:55:40 EST 2014

STATUS

proposed

reviewed

#8 by Michel Marcus at Mon Feb 10 00:40:02 EST 2014

STATUS

editing

proposed

#7 by Michel Marcus at Mon Feb 10 00:38:43 EST 2014

CROSSREFS

Cf. A125704, A128487.

Discussion

Mon Feb 10

00:40

Michel Marcus: First term is a(2) and 11th term is a(12) hence offset is 2

#6 by Michel Marcus at Mon Feb 10 00:36:45 EST 2014

DATA

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

OFFSET

1,2,1

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

KEYWORD

more,nonn,changed

AUTHOR

Leroy Quet , Mar 08 2007

EXTENSIONS

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

STATUS

approved

editing

#5 by N. J. A. Sloane at Wed Feb 05 20:18:30 EST 2014

AUTHOR

_Leroy Quet _ Mar 08 2007

Discussion

Wed Feb 05

20:18

OEIS Server: https://oeis.org/edit/global/2118

#4 by N. J. A. Sloane at Sat Oct 02 03:00:00 EDT 2010

LINKS

Leroy Quet, <a href="http://www.prism-of-spirals.net/">Home Page</a> (listed in lieu of email address)

KEYWORD

more,nonn,new

#3 by N. J. A. Sloane at Fri Jan 09 03:00:00 EST 2009

LINKS

Leroy Quet, <a href="http://www.prism-of-spirals.net/">Home Page</a> (listed in lieu of email address)

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.

KEYWORD

more,nonn,new

AUTHOR

Leroy Quet (qq-quet(AT)mindspring.com), Mar 08 2007

#2 by N. J. A. Sloane at Sat Nov 10 03:00:00 EST 2007

NAME

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

KEYWORD

more,nonn,new

#1 by N. J. A. Sloane at Fri May 11 03:00:00 EDT 2007

NAME

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

DATA

3, 4, 7, 6, 10, 8, 15, 13, 18, 12, 22

OFFSET

1,1

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.

CROSSREFS

Cf. A128487.

KEYWORD

more,nonn

AUTHOR

Leroy Quet (qq-quet(AT)mindspring.com), Mar 08 2007

STATUS

approved