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A064427 (Number of primes <= n - 1) + n. 3
1, 2, 4, 6, 7, 9, 10, 12, 13, 14, 15, 17, 18, 20, 21, 22, 23, 25, 26, 28, 29, 30, 31, 33, 34, 35, 36, 37, 38, 40, 41, 43, 44, 45, 46, 47, 48, 50, 51, 52, 53, 55, 56, 58, 59, 60, 61, 63, 64, 65, 66, 67, 68, 70, 71, 72, 73, 74, 75, 77, 78, 80, 81, 82 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Complement of set {A(prime(n)+n)} = {A014688(n)} = {A(A000040(n)+A000027(n))}. [Jaroslav Krizek, Dec 10 2009]

a(n) = numbers m such that are not the sum of k-th prime and k for any k >= 1. [Jaroslav Krizek, Dec 10 2009]

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Carlos Rivera, Puzzle 821. Prime numbers and complementary sequences, Prime Puzzles.

Eric Weisstein's World of Mathematics, Prime Counting Function

Wikipedia, Prime-counting function

FORMULA

For n > 1: a(n) = A000720(n - 1) + n.

MATHEMATICA

a[n_] := PrimePi[a[n-1]]+n; a[1]=1

Table[PrimePi[n-1]+n, {n, 60}] (* Harvey P. Dale, Apr 03 2015 *)

PROG

(Haskell)

a064427 1 = 1

a064427 n = a000720 (n - 1) + toInteger n

-- Reinhard Zumkeller, Apr 17 2012

(PARI) a(n) = if (n==1, 1, primepi(n-1)+n); \\ Michel Marcus, Feb 13 2016

(MAGMA) [1] cat [#PrimesUpTo(n-1)+n: n in [2..100]]; // Vincenzo Librandi, Feb 13 2016

CROSSREFS

Cf. A095117.

Sequence in context: A026516 A186493 A111094 * A183569 A248612 A247000

Adjacent sequences:  A064424 A064425 A064426 * A064428 A064429 A064430

KEYWORD

nonn

AUTHOR

Santi Spadaro, Sep 30 2001

EXTENSIONS

Definition improved by Reinhard Zumkeller, Apr 16 2012

STATUS

approved

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Last modified May 2 19:17 EDT 2016. Contains 272345 sequences.