A107836 - OEIS

A107836

Slowest increasing sequence where a(n)+(first digit of a(n)) is prime.

1, 10, 12, 16, 18, 21, 27, 29, 34, 38, 43, 49, 54, 56, 61, 65, 67, 72, 76, 81, 89, 92, 94, 98, 100, 102, 106, 108, 112, 126, 130, 136, 138, 148, 150, 156, 162, 166, 172, 178, 180, 190, 192, 196, 198, 209, 221, 225, 227, 231, 237, 239, 249, 255, 261, 267, 269, 275

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

EXAMPLE

1 + 1 = 2, which is prime; 10 + 1 = 11, which is prime; 12 + 1 = 13, which is prime; 16 + 1 = 17, which is prime; 18 + 1 = 19, which is prime; 21 + 2 = 23, which is prime; etc.

MAPLE

select(t -> isprime(t + floor(t/10^ilog10(t))), [$1..1000]); # Robert Israel, May 05 2020

MATHEMATICA

Select[ Range[280], PrimeQ[ # + IntegerDigits[ # ][[1]]] &] (* Robert G. Wilson v, Jun 14 2005 *)

PROG

(Python)

from sympy import isprime

from itertools import count, islice

def agen(): # generator of terms

an = 0

while True:

an = next(k for k in count(an+1) if isprime(k + int(str(k)[0])))

yield an

print(list(islice(agen(), 58))) # Michael S. Branicky, Oct 03 2024

CROSSREFS

Sequence in context: A057485 A162825 A376372 * A096128 A334939 A063192

Adjacent sequences: A107833 A107834 A107835 * A107837 A107838 A107839

KEYWORD

base,easy,nonn

AUTHOR

Eric Angelini, Jun 11 2005

EXTENSIONS

Edited, corrected and extended by Robert G. Wilson v, Jun 14 2005

STATUS

approved