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A115288 a(n) is the smallest number representable in exactly n ways as a sum of 2 triangular numbers and one square (each of them >= 0). 4
0, 1, 4, 7, 10, 16, 22, 25, 64, 46, 70, 67, 92, 85, 160, 115, 106, 136, 200, 157, 190, 172, 256, 235, 568, 277, 370, 337, 400, 367, 340, 550, 556, 442, 1102, 445, 472, 631, 610, 535, 682, 697, 652, 1075, 956, 850, 1984, 865, 1172, 997, 862, 1081, 1462, 1135, 1060 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..55.

EXAMPLE

a(4)=7 since 7 can be expressed in 4 ways, 7= T(3)+T(1)+0^2 = T(3)+T(0)+1^2 = T(2)+T(0)+2^2 = T(2)+T(2)+1^2 and none of the numbers from 0 to 6 can be expressed in 4 ways.

MATHEMATICA

V=Table[0, {i, 2500}]; T[n]:=n(n+1)/2; Do[a=T[i]+T[j]+k^2; If[a<2500, V[[a+1]]++ ], {i, 0, 71}, {j, 0, i}, {k, 0, 50}]; Table[Position[V, z][[1, 1]]-1, {z, 60}]

CROSSREFS

Cf. A115289, A000437, A061262.

Sequence in context: A177965 A179209 A168565 * A180080 A153003 A213484

Adjacent sequences:  A115285 A115286 A115287 * A115289 A115290 A115291

KEYWORD

nonn

AUTHOR

Giovanni Resta, Jan 19 2006

STATUS

approved

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Last modified December 4 16:52 EST 2016. Contains 278750 sequences.