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A106155 Numbers k > 2 such that prime(k)# + (prime(k+1))^2 or prime(k+1)# - (prime(k+2))^2 is prime or both are primes. 1

%I #15 Jun 10 2023 03:09:12

%S 3,4,5,6,7,10,12,13,19,26,28,41,66,73,76,78,85,371,437,513,661,726,

%T 924,1063,1331,1380,1422,1602,1947,1963,3091,3295,3401

%N Numbers k > 2 such that prime(k)# + (prime(k+1))^2 or prime(k+1)# - (prime(k+2))^2 is prime or both are primes.

%e 2*3*5 + 7*7 = 79 prime as 2*3*5*7 - 11*11 = 89 prime so a(1)=3.

%e 2*3*5*7 + 11*11 = 331 prime as 2*3*5*7*11 -13*13 = 2141 prime so a(2)=4.

%e 2*3*5*7*11 + 13*13 = 2479 = 37*67 composite.

%e 2*3*5*7*11*13 - 17*17 = 29471 prime so a(3)=5.

%Y Cf. A002110, A038767.

%K more,nonn

%O 1,1

%A _Pierre CAMI_, May 08 2005

%E a(20)-a(30) from _Donovan Johnson_, Apr 27 2008

%E a(31)-a(33) from _Michael S. Branicky_, Jun 09 2023

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Last modified August 14 04:31 EDT 2024. Contains 375146 sequences. (Running on oeis4.)