a(n) is the number of essentially different ways in which the integers 1,2,3,...,n can be arranged in a sequence such that all pairs of adjacent integers sum to a prime number. Rotations and reversals are counted only once.
A073452
a(n) is the number of essentially different ways in which the integers 1,2,3,...,n can be arranged in a sequence such that all pairs of adjacent integers sum to a prime number. Rotations and reversals are counted only once.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =3a(6) =12a(7) =16a(8) =70a(9) =232a(10) =1072a(11) =3136a(12) =11648a(13) =18388a(14) =95772a(15) =452136a(16) =2047488a(17) =5565488a(18) =22802028a(19) =60841609a(20) =337801784a(21) =2116714332a(22) =11425028900a(23) =69023494710a(24) =429917269469
External references
- oeis: A073452