Number of permutations f of {1,...,n} such that prime(k)*prime(f(k)) - 2 is prime for every k = 1,...,n.

A321855

Number of permutations f of {1,...,n} such that prime(k)*prime(f(k)) - 2 is prime for every k = 1,...,n.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =3a(4) =5a(5) =12a(6) =2a(7) =3a(8) =65a(9) =248a(10) =448a(11) =1792a(12) =4288a(13) =6468a(14) =27068a(15) =29752a(16) =106066a(17) =447982a(18) =1250762a(19) =6304196a(20) =46613084a(21) =126391780a(22) =504582496a(23) =2270372946a(24) =3028652541a(25) =8941959118a(26) =36442298864a(27) =175008626450a(28) =318369805106

External references