|
%I #5 Sep 10 2016 15:57:46
%S 10,24,126,294,858,1704,3528,5082,10296,11526,18894,22320,32208,36666,
%T 38976,51744,57330,72618,79212,96996,120684,175968,186162,212922,
%U 271914,324300,359382,381282,411504,434790,655278,674856,684726,735282,776904
%N Sum of staircase twin primes according to the rule: top * bottom - next top.
%C While there is multiplication and subtraction in the generation of this sequence, it is still called a sum because the arithmetic processes -,*,/ are derived from addition.
%F We list the twin primes in staircase fashion as in A135283. Then a(n) = tl(n) * tu(n) + (-tl(n+1)).
%F a(n) = A037074(n) -A001359(n+1). - _R. J. Mathar_, Sep 10 2016
%o (PARI) g(n) = for(x=1,n,y=twinu(x) * twinl(x) - twinl(x+1);print1(y",")) twinl(n) = / *The n-th lower twin prime. */ { local(c,x); c=0; x=1; while(c<n, if(ispseudoprime(prime(x)+2),c++); x++; ); return(prime(x-1)) } twinu(n) = /* The n-th upper twin prime. */ { local(c,x); c=0; x=1; while(c<n, if(isprime(prime(x)+2),c++); x++; ); return(prime(x)) }
%K nonn
%O 1,1
%A _Cino Hilliard_, Dec 03 2007
|
