OFFSET
1,3
COMMENTS
Numbers n such that (310*10^n + 23)/9 is prime.
Numbers n such that digit 3 followed by n >= 0 occurrences of digit 4 followed by digit 7 is prime.
Numbers corresponding to terms <= 757 are certified primes.
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
LINKS
FORMULA
a(n) = A102969(n) - 1.
EXAMPLE
347 is prime, hence 1 is a term.
MATHEMATICA
For[n=0, n <= 4000, n++, If[PrimeQ[(310*10^n + 23)/9], Print[n]]] (Steinerberger)
PROG
(PARI) a=37; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-23)
(PARI) for(n=0, 1500, if(isprime((310*10^n+23)/9), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 20 2004
EXTENSIONS
a(5) from Stefan Steinerberger, Feb 04 2006
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
a(9)-a(10) from Kamada data by Ray Chandler, May 01 2015
STATUS
approved