The smallest prime p such that tau(p-1) + tau(p+1) = prime(n), or 0 if no such prime exists; where tau(k) is the number of divisors of k.

A189536

The smallest prime p such that tau(p-1) + tau(p+1) = prime(n), or 0 if no such prime exists; where tau(k) is the number of divisors of k.

Terms

    a(0) =0a(1) =2a(2) =3a(3) =5a(4) =17a(5) =37a(6) =101a(7) =0a(8) =401a(9) =3137a(10) =4357a(11) =62501a(12) =21317a(13) =16901a(14) =1008017a(15) =15877a(16) =1020101a(17) =33857a(18) =69697a(19) =14401a(20) =331777a(21) =78401a(22) =32401a(23) =57601a(24) =828101a(25) =40195601a(26) =32080897a(27) =3326977a(28) =876097a(29) =476101

External references