OFFSET
1,3
COMMENTS
These are primes of the form 91 + 42*k + 6*k^2.
FORMULA
a(n) = Sum_{k=1..n} A218211(k).
MATHEMATICA
n = 0; cnt = 0; Table[While[n++; p = 91 + 42*n + 6*n^2; p < 10^e, If[PrimeQ[p], cnt++]]; n--; cnt, {e, 14}] (* T. D. Noe, Oct 23 2012, edited by Michael De Vlieger, Feb 18 2018 *)
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
Martin Renner, Oct 23 2012
EXTENSIONS
a(13)-a(21) from Chai Wah Wu, Feb 12 2018
Changed terms (as A218211(2) is reverted back to 0) by Chai Wah Wu, Feb 13 2018
STATUS
approved