A077648 - OEIS

A077648

Initial digits of prime numbers.

2, 3, 5, 7, 1, 1, 1, 1, 2, 2, 3, 3, 4, 4, 4, 5, 5, 6, 6, 7, 7, 7, 8, 8, 9, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5

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

OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A000030(A000040(n)).

MATHEMATICA

Table[First[IntegerDigits[Prime[n]]], {n, 1, 120}]

PROG

(Magma) [Intseq(p)[#Intseq(p)]: p in PrimesUpTo(600)]; // Bruno Berselli, Feb 14 2013

(PARI) a(n) = digits(prime(n))[1]; \\ Michel Marcus, Feb 11 2017