A198277 a(n) is the smallest prime such that exactly n prime pairs (p,q) exist with a(n) = p * q + p + q.

2, 11, 23, 71, 239, 719, 2879, 5039, 1439, 10079, 37799, 126719, 55439, 110879, 181439, 191519, 166319, 635039, 514079, 665279, 1330559, 907199, 3243239, 831599, 2948399, 6320159, 4989599, 15301439, 14137199, 5266799, 11531519, 8315999, 23284799, 17463599, 45208799, 52390799, 34594559, 111767039, 95633999, 117976319, 70685999, 68468399

Offset: 0

Author

Reinhard Zumkeller, Oct 23 2011

Keywords

• nonn

Comments

A067432(A049084(a(n))) = n and A067432(A049084(m)) <> n for m < a(n).

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 0..115
• Reinhard Zumkeller, Illustration of initial terms

Programs

Haskell

import Data.List (elemIndex)
import Data.Maybe (fromJust)
a198277 n = a000040 . (+ 1) . fromJust $ elemIndex n a067432_list

PARI

ct(n)=sumdiv(n+1,d,if(d^2>n,0, isprime(d-1)&&isprime(n\d)))
v=vector(60);forprime(p=2,1e9, t=ct(p);if(t && !v[t], v[t]=p; print(t" "p))); v \\ with 0's for unknown; Charles R Greathouse IV, Jul 24 2013

Extensions

a(27)-a(33) from Donovan Johnson, Oct 24 2011

a(34)-a(41) from Charles R Greathouse IV, Jul 24 2013