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

Offset: 1

Author

Labos Elemer, Nov 19 2002

Keywords

• base
• nonn

Links

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

Crossrefs

Cf. A000030, A000040.

Programs

Magma

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

Mathematica

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

PARI

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

Python

from sympy import prime
def A077648(n): return int(str(prime(n))[0]) # Chai Wah Wu, Oct 16 2024

Formula

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