OFFSET
1,2
COMMENTS
Indices of the triangular numbers in A147846.
Integers k such that k or k+1 is prime. - Giovanni Teofilatto, Mar 05 2010
For a given common difference d, there always exists a longest possible arithmetic progression (AP) of primes, and the number of elements k in this AP of primes is necessarily a term of this sequence. See A123556 for explanations. - Bernard Schott, Mar 18 2023
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000.
Diophante, A1880. NP (Nombres Premiers) en PA (Progression Arithmétique) (in French).
Wikipedia, Primes in arithmetic progression.
MATHEMATICA
{#-1, #}&/@Prime[Range[40]]//Flatten//Union (* Harvey P. Dale, Dec 21 2018 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Giovanni Teofilatto, Mar 02 2010
EXTENSIONS
Definition corrected and sequence extended by R. J. Mathar, Feb 24 2010, Mar 05 2010
STATUS
approved