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A292611
Skip 3 triangle numbers, take 1 triangle number, skip 4 triangle numbers, take 2 triangle numbers, skip 5 triangle numbers, take 3 triangle numbers, ...
3
10, 45, 55, 136, 153, 171, 325, 351, 378, 406, 666, 703, 741, 780, 820, 1225, 1275, 1326, 1378, 1431, 1485, 2080, 2145, 2211, 2278, 2346, 2415, 2485, 3321, 3403, 3486, 3570, 3655, 3741, 3828, 3916, 5050, 5151, 5253, 5356, 5460, 5565, 5671, 5778, 5886, 7381
OFFSET
1,1
LINKS
FORMULA
Sum_{n = (k-1)*k/2+1 .. k*(k+1)/2} a(n) = Sum_{n = (k+1)*(k+2)/2-2 .. (k+2)*(k+3)/2-3} A292610(n) = A222716(k+1) for k > 0.
EXAMPLE
k| A292610(n) | a(n) | Sum
---------------------------------------------------------------------------------------
0| (= 0)
1| 1 + 3 + 6 = 10 (= 10)
2| 15 + 21 + 28 + 36 = 45 + 55 (= 100)
3| 66 + 78 + 91 + 105 + 120 = 136 + 153 + 171 (= 460)
4| 190 + 210 + 231 + 253 + 276 + 300 = 325 + 351 + 378 + 406 (= 1460)
5| 435 + 465 + 496 + 528 + 561 + 595 + 630 = 666 + 703 + 741 + 780 + 820 (= 3710)
MATHEMATICA
Block[{s = Array[{#, # + 3} &, 11] - 1, r}, r = PolygonalNumber@ Range@ Total@ Flatten@ s; Map[Function[{a, b}, {First@ #, Set[r, Drop[Last@ #, b]]} &@ TakeDrop[r, a]] @@ # &, s][[All, 1]] // Flatten] (* Michael De Vlieger, Sep 25 2017 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Sep 20 2017
STATUS
approved