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A308513 Sum of the largest side lengths of all integer-sided triangles with perimeter n whose smallest side length is prime. 1
0, 0, 0, 0, 0, 2, 3, 3, 7, 8, 14, 10, 17, 12, 25, 20, 36, 31, 50, 35, 63, 47, 79, 62, 98, 80, 120, 87, 130, 94, 140, 101, 161, 120, 185, 142, 212, 167, 255, 209, 304, 257, 359, 289, 397, 324, 438, 362, 482, 403, 546, 439, 589, 478, 635, 520, 703, 585, 777 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,6
LINKS
Wikipedia, Integer Triangle
FORMULA
a(n) = Sum_{k=1..floor(n/3)} Sum_{i=k..floor((n-k)/2)} sign(floor((i+k)/(n-i-k+1))) * A010051(k) * (n-i-k).
MATHEMATICA
Table[Sum[Sum[(n - i - k) (PrimePi[k] - PrimePi[k - 1]) Sign[Floor[(i + k)/(n - i - k + 1)]], {i, k, Floor[(n - k)/2]}], {k, Floor[n/3]}], {n, 100}]
CROSSREFS
Sequence in context: A335050 A062761 A117524 * A045683 A343031 A157531
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Jun 02 2019
STATUS
approved

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Last modified May 18 14:58 EDT 2024. Contains 372641 sequences. (Running on oeis4.)