OFFSET
1,1
COMMENTS
a(126) is unknown; it's known to either be 0 or have more than 152 digits.
a(126) has 277 digits. - J. Lowell, Jan 01 2023
a(161) is unknown; it is either 0 or has more than 333 digits. - J. Lowell and Sean A. Irvine, Feb 04 2023
LINKS
Sean A. Irvine, Table of n, a(n) for n = 1..160
Sean A. Irvine Java program (github)
EXAMPLE
a(17) = 3571 because:
34 + 1 = 35 is composite with smallest prime factor 5, and 34*5 = 170;
170 + 1 = 171 is composite with smallest prime factor 3, and 170*3 = 510;
510 + 1 = 511 is composite with smallest prime factor 7, and 510*7 = 3570;
3570 + 1 = 3571 is prime.
If A359444 has a term k that is one less than a prime, then a(161) = k + 1; otherwise, a(161) = 0.
PROG
(PARI) a(n) = {my(x = 2*n); while (! isprime(x+1), x = x*vecmin(factor(x+1)[, 1]); ); x+1; } \\ Michel Marcus, Jun 07 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
J. Lowell, Jun 06 2017
EXTENSIONS
More terms from Michel Marcus, Jun 07 2017
Name simplified by Jon E. Schoenfield, Jan 01 2023
STATUS
approved