A386964 a(1) = prime(1) = 2, a(n) = 10*a(n-1) + (prime(n) mod 10).

2, 23, 235, 2357, 23571, 235713, 2357137, 23571379, 235713793, 2357137939, 23571379391, 235713793917, 2357137939171, 23571379391713, 235713793917137, 2357137939171373, 23571379391713739, 235713793917137391, 2357137939171373917, 23571379391713739171, 235713793917137391713

Offset

1,1

Links

Michael S. Branicky, Table of n, a(n) for n = 1..1000

Formula

a(n) = concatenation of A007652(1)..A007652(n).

Maple

a:= proc(n) option remember; `if`(n<1, 0, a(n-1)*10+irem(ithprime(n), 10)) end:
seq(a(n), n=1..21);  # Alois P. Heinz, Aug 12 2025

Mathematica

a[1]=2; a[n_]:=10a[n-1]+Mod[Prime[n], 10]; Array[a, 21] (* James C. McMahon, Aug 12 2025 *)

Prog

(Python)
from sympy import nextprime
from itertools import islice
def A386964(): # generator of terms
    an = pn = 2
    while True:
        yield an
        an = 10*an + (pn:=nextprime(pn))%10
print(list(islice(A386964(), 21)))

Crossrefs

Cf. A007652, A276481.

Sequence in context: A301339 A294268 A118385 * A098739 A287353 A091762

Adjacent sequences: A386961 A386962 A386963 * A386965 A386966 A386967

Keyword

nonn,base,easy

Author

Michael S. Branicky, Aug 11 2025

Status

approved