OFFSET
1,1
COMMENTS
a(n) = n if n is a term of A001043 (on graph this corresponds to the lower bound).
LINKS
Michel Marcus, Table of n, a(n) for n = 1..10000
Zak Seidov, Table of {n, i, a(n), k=a(n)/n} for n = 1..1000
FORMULA
a(n) = smallest number, of the form k*n (k >= 1), that is the sum of 2 successive primes.
EXAMPLE
5 is a term because prime(1) + prime(2) = 2 + 3 = 5 = 5*1 (k = 5),
8 is a term because prime(2) + prime(3) = 3 + 5 = 8 = 4*2 (k = 4),
198 is a term because prime(25) + prime(26) = 97 + 101 = 198 = 18*11 (k = 18).
PROG
(PARI) is(n) = (precprime((n-1)/2) + nextprime(n/2) == n) && (n>2); \\ A001043
a(n) = my(k=1); while (!is(k*n), k++); k*n; \\ Michel Marcus, Oct 06 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Nov 28 2014
STATUS
approved