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

1,1

Links

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

Example

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

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 *)

Crossrefs

Cf. A090482, A000005.

Sequence in context: A347192 A335325 A189828 * A094342 A164641 A058982

Adjacent sequences: A090478 A090479 A090480 * A090482 A090483 A090484

Keyword

nonn

Author

Amarnath Murthy, Dec 02 2003

Extensions

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

Status

approved