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 A087820 Primes P of the form P=(j*P(i)#)/2 - 2 such that P+4 is the next prime, where j is odd, 0 < j < P(i+1), P(i) = i-th prime, P(i)# = i-th primorial (A002110). 3
 7, 13, 43, 103, 313, 3463, 15013, 195193, 225223, 765763, 4339333, 3011753743, 9704539843, 100280245063, 2707566616753, 124286232650865283, 150451755314205343, 10760571195298599673, 211829530101735290743 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS I think I have a proof that the sequence is infinite. LINKS Table of n, a(n) for n=0..18. EXAMPLE (27*2*3*5*7*11*13*17*19*23)/2 - 2 = 3011753743 and (27*2*3*5*7*11*13*17*19*23)/2 + 2 = 3011753747 are gap 4 primes, so j=27, i=9, P(i)=23. CROSSREFS Cf. A087821, A087822, etc. Sequence in context: A361914 A047977 A139403 * A272032 A023286 A287685 Adjacent sequences: A087817 A087818 A087819 * A087821 A087822 A087823 KEYWORD nonn AUTHOR Pierre CAMI, Oct 06 2003 EXTENSIONS More terms from Ray Chandler, Oct 19 2003 STATUS approved

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Last modified August 7 08:38 EDT 2024. Contains 375008 sequences. (Running on oeis4.)