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

%I A386964 #14 Aug 12 2025 20:33:55
%S A386964 2,23,235,2357,23571,235713,2357137,23571379,235713793,2357137939,
%T A386964 23571379391,235713793917,2357137939171,23571379391713,
%U A386964 235713793917137,2357137939171373,23571379391713739,235713793917137391,2357137939171373917,23571379391713739171,235713793917137391713
%N A386964 a(1) = prime(1) = 2, a(n) = 10*a(n-1) + (prime(n) mod 10).
%H A386964 Michael S. Branicky, <a href="/A386964/b386964.txt">Table of n, a(n) for n = 1..1000</a>
%F A386964 a(n) = concatenation of A007652(1)..A007652(n).
%p A386964 a:= proc(n) option remember; `if`(n<1, 0, a(n-1)*10+irem(ithprime(n), 10)) end:
%p A386964 seq(a(n), n=1..21);  # _Alois P. Heinz_, Aug 12 2025
%t A386964 a[1]=2;a[n_]:=10a[n-1]+Mod[Prime[n],10];Array[a,21] (* _James C. McMahon_, Aug 12 2025 *)
%o A386964 (Python)
%o A386964 from sympy import nextprime
%o A386964 from itertools import islice
%o A386964 def A386964(): # generator of terms
%o A386964     an = pn = 2
%o A386964     while True:
%o A386964         yield an
%o A386964         an = 10*an + (pn:=nextprime(pn))%10
%o A386964 print(list(islice(A386964(), 21)))
%Y A386964 Cf. A007652, A276481.
%K A386964 nonn,base,easy
%O A386964 1,1
%A A386964 _Michael S. Branicky_, Aug 11 2025