login
a(n) + a(n-1) = n-th prime.
9

%I #40 Feb 21 2022 00:54:57

%S 1,1,2,3,4,7,6,11,8,15,14,17,20,21,22,25,28,31,30,37,34,39,40,43,46,

%T 51,50,53,54,55,58,69,62,75,64,85,66,91,72,95,78,101,80,111,82,115,84,

%U 127,96,131,98,135,104,137,114,143,120,149,122,155,126,157,136,171,140,173

%N a(n) + a(n-1) = n-th prime.

%C After the initial 1,1, this sequence contains no duplicate values: terms thereafter have opposite parity, and a(n+2) > a(n). Do even and odd values trade the lead infinitely often? (We would expect them to if we model their difference as a random walk.) - _Franklin T. Adams-Watters_, Jan 25 2010

%H T. D. Noe, <a href="/A036467/b036467.txt">Table of n, a(n) for n = 0..2000</a>

%t a[n_] := Abs[1+Sum[(-1)^(k+1)*Prime[k], {k, 2, n}]]; a /@ Range[0, 65] (* _Jean-François Alcover_, Apr 22 2011 *)

%t t={1,1};Do[AppendTo[t,NextPrime[t[[-2]]+t[[-1]]]-t[[-1]]],{n,64}];t (* _Vladimir Joseph Stephan Orlovsky_, Jan 26 2012 *)

%t Transpose[NestList[{First[#]+1,Prime[First[#]+1]-Last[#]}&,{0,1},70]][[2]] (* _Harvey P. Dale_, Sep 14 2012 *)

%o (Magma) [n lt 2 select 1 else NthPrime(n)-NthPrime(n-1)+Self(n-1): n in [0..65]]; // _Bruno Berselli_, Jun 18 2011

%o (PARI) print1(t=1);forprime(p=2,1e3,print1(", ",t=p-t)) \\ _Charles R Greathouse IV_, Jun 18, 2011

%o (Haskell)

%o a036467 n = a036467_list !! n

%o a036467_list = 1 : zipWith (-) a000040_list a036467_list

%o -- _Reinhard Zumkeller_, Nov 02 2011

%Y Cf. A001223, A008347.

%K nonn,easy,nice

%O 0,3

%A _Maghraoui Abdelkader_

%E More terms from _Jud McCranie_