Number of permutations f of {1,...,n} such that prime(k) + prime(f(k)) + 1 is prime for every k = 1,...,n.

A321727

Number of permutations f of {1,...,n} such that prime(k) + prime(f(k)) + 1 is prime for every k = 1,...,n.

Terms

    a(0) =1a(1) =1a(2) =1a(3) =2a(4) =6a(5) =10a(6) =31a(7) =76a(8) =696a(9) =4294a(10) =5772a(11) =8472a(12) =128064a(13) =147960a(14) =1684788a(15) =26114739a(16) =523452320a(17) =1029877159a(18) =1772807946a(19) =28736761941a(20) =19795838613a(21) =31445106424

External references