Number of permutations p of (1..n) such that k+p(k) is a semiprime for 1 <= k <= n.

A276735

Number of permutations p of (1..n) such that k+p(k) is a semiprime for 1 <= k <= n.

Terms

    a(0) =1a(1) =0a(2) =0a(3) =1a(4) =1a(5) =3a(6) =5a(7) =12a(8) =87a(9) =261a(10) =324a(11) =1433a(12) =5881a(13) =37444a(14) =196797a(15) =708901a(16) =2020836a(17) =12375966a(18) =105896734a(19) =955344450a(20) =11136621319a(21) =95274505723a(22) =590283352231

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