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 A064799 Sum of n-th prime number and n-th composite number. 7

%I

%S 6,9,13,16,21,25,31,34,39,47,51,58,63,67,72,79,86,89,97,103,106,113,

%T 118,125,135,140,143,149,153,158,173,179,186,189,200,203,211,218,223,

%U 230,237,241,253,256,261,264,277,291,296,299,305,313,316,327,334,341

%N Sum of n-th prime number and n-th composite number.

%C a(n) = A000040(n) + A002808(n). - _Jaroslav Krizek_, Dec 13 2009

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

%H Harry J. Smith, <a href="/A064799/b064799.txt">Table of n, a(n) for n = 1..1000</a>

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

%F a(n) = A171639(n+1). - _Jaroslav Krizek_, Dec 13 2009

%e a(1)=6 because the first prime is 2 and the first composite is 4; 2 + 4 = 6

%e a(2)=9 because prime(2)=3 and composite(2)=6; 3 + 6 = 9.

%o (PARI) nextComp(n)= { if (!isprime(n), return(n)); return(n + 1) } { p=1; c=3; for (n=1, 1000, p=nextprime(p + 1); c=nextComp(c + 1); write("b064799.txt", n, " ", p + c) ) } \\ _Harry J. Smith_, Sep 25 2009

%K nonn,easy

%O 1,1

%A Konstantin Knop (Konstantin(AT)Knop.com), Oct 21 2001

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

%E Offset changed from 0 to 1 by _Harry J. Smith_, Sep 25 2009

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Last modified September 16 12:57 EDT 2019. Contains 327113 sequences. (Running on oeis4.)