login
A078403
Primes whose digital root (A038194) is prime.
10
2, 3, 5, 7, 11, 23, 29, 41, 43, 47, 59, 61, 79, 83, 97, 101, 113, 131, 137, 149, 151, 167, 173, 191, 223, 227, 239, 241, 257, 263, 277, 281, 293, 311, 313, 317, 331, 347, 349, 353, 367, 383, 389, 401, 419, 421, 439, 443, 457, 461, 479, 491, 509, 547, 563, 569
OFFSET
1,1
COMMENTS
Union of A061238, A061240, A061241 and 3. - Ya-Ping Lu, Jan 03 2024
EXAMPLE
59 is a term because 5+9=14, giving (final) iterated sum 1+4=5 and 5 is prime.
MATHEMATICA
Select[ Range[580], PrimeQ[ # ] && PrimeQ[Mod[ #, 9]] &]
Select[Prime[Range[200]], PrimeQ[Mod[#, 9]]&] (* Harvey P. Dale, Aug 20 2017 *)
PROG
(PARI) forprime(p=2, 997, if(isprime(p%9), print1(p, ", ")))
(Python) from sympy import isprime, primerange; [print(p, end = ', ') for p in primerange(2, 570) if isprime(p%9)] # Ya-Ping Lu, Jan 03 2024
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
N. J. A. Sloane, Dec 26 2002
EXTENSIONS
STATUS
approved