|
Search: id:A135283
|
|
|
| A135283 |
|
Sum of staircase twin primes according to the rule: top + bottom + next top. |
|
+0
4
|
|
| 13, 23, 41, 65, 101, 143, 191, 245, 311, 353, 425, 479, 551, 581, 623, 695, 749, 821, 875, 971, 1115, 1271, 1325, 1445, 1613, 1739, 1817, 1877, 1943, 2129, 2441, 2471, 2513, 2597, 2783, 3071, 3113, 3161, 3215, 3335, 3533, 3737, 3845, 3881, 3923, 4067
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
We list the twin primes in staircase fashion as follows.
3
5_5
__7_11
____13_17
_______19_29
__________31_41
_____________.._..
________________tu(n)_tl(n)
______________________tu(n+1)
...
where tl(n) = n-th lower twin prime, tu(n) = n-th upper twin prime. Then a(n) = tl(n) + tu(n) + tl(n+1).
|
|
PROGRAM
|
(PARI) g(n) = for(x=1, n, y=twinu(x)+twinl(x) + twinl(x+1); print1(y", ")) twinl(n) = / *The nth 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 nth upper twin prime. */ { local(c, x); c=0; x=1; while(c<n, if(isprime(prime(x)+2), c++); x++; ); return(prime(x)) }
|
|
CROSSREFS
|
Adjacent sequences: A135280 A135281 A135282 this_sequence A135284 A135285 A135286
Sequence in context: A164434 A164494 A164407 this_sequence A119488 A165350 A112394
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Cino Hilliard (hillcino368(AT)hotmail.com), Dec 02 2007
|
|
|
Search completed in 0.002 seconds
|
