A064799 Sum of n-th prime number and n-th composite number.

6, 9, 13, 16, 21, 25, 31, 34, 39, 47, 51, 58, 63, 67, 72, 79, 86, 89, 97, 103, 106, 113, 118, 125, 135, 140, 143, 149, 153, 158, 173, 179, 186, 189, 200, 203, 211, 218, 223, 230, 237, 241, 253, 256, 261, 264, 277, 291, 296, 299, 305, 313, 316, 327, 334, 341

Offset

1,1

References

Ivan Grischenko, ivansasha(AT)mtu-net.ru, private communication.

Links

Harry J. Smith, Table of n, a(n) for n = 1..1000

Formula

a(n) = prime(n) + composite(n).

From Jaroslav Krizek, Dec 13 2009: (Start)

a(n) = A000040(n) + A002808(n).

a(n) = A171639(n+1). (End)

Example

a(1)=6 because the first prime is 2 and the first composite is 4; 2 + 4 = 6
a(2)=9 because prime(2)=3 and composite(2)=6; 3 + 6 = 9.

Mathematica

Module[{nn=100, cmps}, cmps=Select[Range[nn], CompositeQ]; Total/@Thread[{Prime[Range[ Length[ cmps]]], cmps}]] (* Harvey P. Dale, Mar 31 2024 *)

Prog

(PARI)
nextComp(n)= { if (!isprime(n), return(n)); return(n + 1) }
{ p=1; c=3; for (n=1, 100, p=nextprime(p + 1); c=nextComp(c + 1); print1(p + c, ", ") ) } \\ Harry J. Smith, Sep 25 2009
(Python)
from sympy import prime, composite
def A064799(n): return prime(n)+composite(n) # Chai Wah Wu, Aug 30 2021

Crossrefs

Cf. A000040, A002808, A171639.

Sequence in context: A242874 A284800 A242295 * A236763 A030499 A181428

Adjacent sequences: A064796 A064797 A064798 * A064800 A064801 A064802

Keyword

nonn,easy

Author

Konstantin Knop, Oct 21 2001

Extensions

More terms from Larry Reeves (larryr(AT)acm.org), Nov 12 2001

Offset changed from 0 to 1 by Harry J. Smith, Sep 25 2009

Status

approved