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A340278

Number of partitions of n into 3 parts whose smallest and largest parts are relatively prime.

0, 0, 1, 1, 2, 2, 4, 4, 5, 6, 9, 8, 11, 11, 13, 15, 19, 18, 23, 22, 24, 26, 32, 31, 37, 38, 42, 43, 50, 47, 55, 55, 59, 62, 68, 68, 78, 78, 83, 85, 96, 93, 105, 104, 108, 112, 124, 121, 132, 131, 138, 141, 154, 151, 162, 164, 172, 176, 191, 187, 205, 205, 212, 217, 228, 226

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OFFSET

1,5

LINKS

Table of n, a(n) for n=1..66.

Index entries for sequences related to partitions

FORMULA

a(n) = Sum_{k=1..floor(n/3)} Sum_{i=k..floor((n-k)/2)} floor(1/gcd(k,n-i-k)).

MATHEMATICA

Table[Sum[Sum[Floor[1/GCD[k, n - i - k]], {i, k, Floor[(n - k)/2]}], {k, Floor[n/3]}], {n, 80}]

CROSSREFS

Cf. A023023, A340275, A340276.