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A176747 Triangular numbers and numbers which cannot be represented as a sum of two earlier members of the sequence. 5
0, 1, 3, 5, 6, 10, 14, 15, 21, 23, 28, 32, 36, 40, 45, 52, 55, 66, 74, 78, 82, 86, 91, 105, 113, 117, 120, 124, 136, 153, 155, 166, 171, 184, 190, 197, 201, 209, 210, 217, 228, 231, 247, 253, 276, 278, 300, 311, 325, 349, 351, 378, 390, 406, 435, 439, 465, 474, 496, 516, 518 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..60.

EXAMPLE

5 is the smallest number which is not represented as sum of 2 numbers of the set {0,1,3}. Therefore 5 is in the sequence.

14 is the smallest number which is not represented as sum of 2 numbers of the set {0,1,3,5,6,10}. Therefore 14 is in the sequence.

MAPLE

isA000217 := proc(n) issqr(8*n+1) ; end proc:

A176747 := proc(n) option remember; if n <=1 then n; else for a from procname(n-1)+1 do if isA000217(a) then return a; end if;

isrep := false; for i from 1 to n-1 do for j from i to n-1 do if procname(i)+procname(j) = a then isrep := true; end if; end do: end do: if not isrep then return a; end if; end do: end if; end proc:

seq(A176747(n), n=0..60) ; # R. J. Mathar, Nov 01 2010

CROSSREFS

Cf. A000217, A176744, A176745, A176746.

Sequence in context: A115823 A190721 A112926 * A238488 A230124 A027627

Adjacent sequences:  A176744 A176745 A176746 * A176748 A176749 A176750

KEYWORD

nonn

AUTHOR

Vladimir Shevelev, Apr 25 2010

EXTENSIONS

Definition rephrased, sequence extended beyond 55 by R. J. Mathar, Nov 01 2010

STATUS

approved

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Last modified December 1 14:10 EST 2021. Contains 349430 sequences. (Running on oeis4.)