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A104587 Triangle read by rows, given by the matrix product A * B where A (A094727) = [1; 2, 3; 3, 4, 5; 4, 5, 6, 7; ...] and B = [1; 1, 1; 1, 1, 1; ...] (both are infinite lower triangular matrices with the other terms zero). 0
1, 5, 3, 12, 9, 5, 22, 18, 13, 7, 35, 30, 24, 17, 9, 51, 45, 38, 30, 21, 11, 70, 63, 55, 46, 36, 25, 13, 92, 84, 75, 65, 54, 42, 29, 15, 117, 108, 98, 87, 75, 62, 48, 33, 17, 145, 135, 124, 112, 99, 85, 70, 54, 37, 19, 176, 165, 153, 140, 126, 111, 95, 78, 60, 41, 21 (list; table; graph; refs; listen; history; text; internal format)
OFFSET
0,2
COMMENTS
Left column of the triangle = pentagonal numbers, A000326 (starting with 1).
Row sums = heptagonal pyramidal numbers, A002413.
LINKS
EXAMPLE
Triangle begins:
1;
5, 3;
12, 9, 5;
22, 18, 13, 7;
35, 30, 24, 17, 9;
51, 45, 38, 30, 21, 11;
70, 63, 55, 46, 36, 25, 13;
92, 84, 75, 65, 54, 42, 29, 15;
...
PROG
(PARI) tabl(nn) = {ma = matrix(nn, nn, n, k, (n+k-1)*(k<=n)); mb = matrix(nn, nn, n, k, (k<=n)); mt = ma*mb; for (i=1, nn, for (j=1, i, print1(ma[i, j], ", "); ); print(); ); } \\ Michel Marcus, Mar 03 2014
CROSSREFS
Sequence in context: A141234 A130180 A245288 * A300940 A131939 A205522
KEYWORD
nonn,tabl
AUTHOR
Gary W. Adamson, Mar 17 2005
EXTENSIONS
More terms from Michel Marcus, Mar 03 2014
Edited by Michel Marcus and N. J. A. Sloane, Mar 03 2014
STATUS
approved

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Last modified March 19 06:47 EDT 2024. Contains 370953 sequences. (Running on oeis4.)