A333115 a(n) is the least prime p such that A001222(p+n) = A001222(p-n) = n.

23, 47, 1621, 373, 2352631, 9241, 18235603, 21968759, 27575049743, 2794997, 32503712890637, 304321037, 390917388671861, 277829661054961, 14392115869140641, 442395934703

Offset

2,1

Comments

a(10) <= 311346179693.

a(11) = 2794997.

a(18) > 7*10^12, a(19) = 1040573169683. - Giovanni Resta, Mar 08 2020

Links

Table of n, a(n) for n=2..17.

Example

a(3) = 47 is prime; 47-3 = 44 = 2^2*11 and 47+3 = 50 = 2*5^2 both have 3 prime divisors with multiplicity.

Maple

f:= proc(n) local k;
      for k from n+1+(n mod 2) by 2 to 3*10^6+1 do
        if isprime(k) and numtheory:-bigomega(k-n)=n and
           numtheory:-bigomega(k+n)=n then return k
        fi od;
      FAIL
end proc:
map(f, [$2..7]);

Mathematica

Table[SelectFirst[Prime@ Range@ 2000000, PrimeOmega[#-n] == n && PrimeOmega[#+n] == n &], {n, 2, 8}] (* Robert Price, Sep 16 2020 *)

Prog

(PARI) a(n) = forprime(p=n+1, oo, if(bigomega(p-n)==n && bigomega(p+n)==n, return(p))); \\ Jinyuan Wang, Mar 08 2020

Crossrefs

Cf. A001222.

Sequence in context: A157358 A158238 A328799 * A042056 A087807 A044100

Adjacent sequences: A333112 A333113 A333114 * A333116 A333117 A333118

Keyword

nonn,more

Author

J. M. Bergot and Robert Israel, Mar 07 2020

Extensions

a(8)-a(9) from Jinyuan Wang, Mar 08 2020

a(10)-a(17) from Giovanni Resta, Mar 08 2020

Status

approved