A340062 - OEIS

A340062

Averages k of twin primes such that the sum (with multiplicity) of prime factors of k-1, k and k+1 is a prime power (but not a prime).

39372, 104963700, 116479500, 182003250, 202991022, 231362100

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..6.

EXAMPLE

a(3) = 116479500 is a member because 116579499 and 11657501 are primes and the sum of prime factors of 116579499, 116579500 = 2^2*3*5^3*19*61*67 and 116579501 is 232959169 = 15263^2 where 15263 is prime.

MAPLE

filter:= proc(t)

local r, s, f;

if not(isprime(t-1) and isprime(t+1)) then return false fi;

r:= 2*t+add(s[1]*s[2], s=ifactors(t)[2]);

f:=numtheory:-factorset(r);

nops(f) = 1 and r <> f[1]

end proc:

select(filter, [seq(t, t=6..3*10^8, 6)]);

CROSSREFS

Cf. A001414, A340060.

Sequence in context: A183833 A203875 A252604 * A031823 A205035 A205283

Adjacent sequences: A340059 A340060 A340061 * A340063 A340064 A340065

KEYWORD

nonn,more

AUTHOR

J. M. Bergot and Robert Israel, Dec 27 2020

STATUS

approved