The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A026431 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A026431

a(n) = least positive integer > a(n-1) and not a(i)*a(j)-1 for 1<=i<j<=n.
(history; published version)

#8 by Bruno Berselli at Mon Mar 07 02:55:25 EST 2016

STATUS

reviewed

approved

#7 by Michel Marcus at Sun Mar 06 14:41:13 EST 2016

STATUS

proposed

reviewed

#6 by Ivan Neretin at Sun Mar 06 14:21:50 EST 2016

STATUS

editing

proposed

#5 by Ivan Neretin at Sun Mar 06 14:21:44 EST 2016

LINKS

Ivan Neretin, <a href="/A026431/b026431.txt">Table of n, a(n) for n = 1..1000</a>

MATHEMATICA

a = {1, 2}; used = {a[[1]]*a[[2]] - 1}; Do[k = a[[-1]] + 1; While[MemberQ[used, k], k++]; used = Union[used, k*a - 1]; AppendTo[a, k], {n, 3, 60}]; a (* Ivan Neretin, Mar 06 2016 *)

CROSSREFS

Similar sequences with different starting conditions: A026432 (1,3), A026433 (2,3), A026434 (1,4), A026435 (2,4), A026436 (3,4).

STATUS

approved

editing

#4 by Russ Cox at Fri Mar 30 18:56:06 EDT 2012

AUTHOR

Clark Kimberling (ck6(AT)evansville.edu)

Clark Kimberling

Discussion

Fri Mar 30

18:56

OEIS Server: https://oeis.org/edit/global/285

#3 by N. J. A. Sloane at Sat Sep 13 03:00:00 EDT 2003

KEYWORD

nonn,new

nonn

AUTHOR

Clark Kimberling, (ck6(AT)evansville.edu)

#2 by N. J. A. Sloane at Fri May 16 03:00:00 EDT 2003

KEYWORD

nonn,new

nonn

AUTHOR

Clark Kimberling, ck6@cedar.(AT)evansville.edu

#1 by N. J. A. Sloane at Sat Dec 11 03:00:00 EST 1999

NAME

a(n) = least positive integer > a(n-1) and not a(i)*a(j)-1 for 1<=i<j<=n.

DATA

1, 2, 3, 4, 6, 8, 9, 10, 12, 13, 14, 16, 18, 20, 21, 22, 24, 28, 30, 32, 33, 34, 36, 37, 40, 42, 44, 45, 46, 48, 49, 50, 52, 54, 56, 57, 58, 60, 61, 64, 66, 68, 69, 70, 72, 74, 75, 76, 78, 80, 81, 82, 84, 85, 86, 88, 90, 92, 93, 94

OFFSET

1,2

KEYWORD

nonn

AUTHOR

Clark Kimberling, ck6@cedar.evansville.edu

STATUS

approved