A090481 Primes p such that tau(p-1)+tau(p+1) is larger than for any previous term. (Smallest prime sandwiched between more composite numbers.)

2, 3, 5, 7, 11, 17, 19, 29, 41, 71, 179, 181, 239, 419, 701, 839, 881, 1259, 1871, 2161, 2521, 4159, 5039, 7561, 10079, 13441, 13859, 20161, 22679, 30241, 35281, 45361, 55439, 65519, 110879, 138599, 151201, 166319, 226799, 262079, 327599, 332641

Offset: 1

Author

Amarnath Murthy, Dec 02 2003

Keywords

• nonn

Examples

			17 follows 11 and 13 is not a term as tau(10) + tau(12) = tau(12) + tau(14) = 10.
		

Links

• Donovan Johnson, Table of n, a(n) for n = 1..100

Crossrefs

Cf. A090482, A000005.

Programs

Mathematica

a = {}; t = 0; Do[p = Prime[n]; s = DivisorSigma[0, p - 1] + DivisorSigma[0, p + 1]; If[s > t, t = s; AppendTo[a, p]], {n, 1, 10^5}]; a (* Robert G. Wilson v, Dec 04 2003 *)

Extensions

More terms from Robert G. Wilson v, Dec 04 2003