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A114031 Group the triangular numbers so that the n-th group sum is a multiple of n. 1, (3, 6, 10, 15), (21), (28), (36, 45, 55, 66, 78), (91, 105, 120, 136, 153, 171, 190), ... Sequence contains the group sums. 3
1, 34, 21, 28, 280, 966, 210, 760, 9180, 2710, 990, 9624, 18876, 11060, 2415, 119696, 5253, 105876, 159600, 19600, 215460, 150700, 256496, 145944, 397575, 93314, 491967, 56644, 932814, 984150, 307706, 3538080, 611094, 139876, 1021580, 152100 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..36.

MAPLE

A000217 := proc(n) option remember ; n*(n+1)/2 ; end: A114031 := proc(n) local strt, su, len, i; strt := 1 ; for su from 1 to n do len := 1; while add( A000217(strt+i), i=0..len-1) mod su <> 0 do len := len+1 ; od ; if su = n then RETURN( add( A000217(strt+i), i=0..len-1) ) ; else strt := strt+len ; fi ; od ; end: for n from 1 to 80 do printf("%d, ", A114031(n)) ; od ; # R. J. Mathar, May 10 2007

CROSSREFS

Cf. A114032, A114033.

Sequence in context: A033354 A033972 A298086 * A133733 A214038 A070727

Adjacent sequences:  A114028 A114029 A114030 * A114032 A114033 A114034

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Nov 13 2005

EXTENSIONS

More terms from R. J. Mathar, May 10 2007

STATUS

approved

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Last modified September 23 20:42 EDT 2021. Contains 347617 sequences. (Running on oeis4.)