|
Search: id:A078646
|
|
|
| A078646 |
|
Number of representations of n as a sum of two primes that are congruent modulo 3. |
|
+0
3
|
|
| 0, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 2, 0, 0, 1, 2, 0, 2, 0, 0, 1, 1, 0, 3, 0, 0, 0, 2, 0, 2, 0, 0, 1, 2, 0, 3, 0, 0, 1, 3, 0, 3, 0, 0, 1, 2, 0, 4, 0, 0, 1, 2, 0, 4, 0, 0, 0, 2, 0, 4, 0, 0, 1, 4, 0, 4, 0, 0, 0, 4, 0, 4, 0, 0, 1, 4, 0, 4, 0, 0, 1, 3, 0, 5, 0, 0, 0, 3, 0, 5, 0, 0, 1, 4, 0
(list; graph; listen)
|
|
|
OFFSET
|
1,22
|
|
|
EXAMPLE
|
22 can be written in two ways as the sum of two congruent primes modulo 3: 22 = 5 + 17 (5 = 17 mod 3) and 22 = 11 + 11 (order of addition is ignored). Hence a(22) = 2.
|
|
MATHEMATICA
|
f[n_] := Module[{a, d, i}, a = {}; u = Floor[n/2]; For[i = 1, i <= u, i++, If[PrimeQ[i] && PrimeQ[n - i] && Mod[i, 3] != Mod[n - i, 3], a = Append[a, {n, i, n - i}]]]; a]; Table[Length[f[n]], {n, 1, 200}]
|
|
CROSSREFS
|
Cf. A074169, A078647, A078648.
Sequence in context: A100563 A087773 A025867 this_sequence A035217 A105964 A001899
Adjacent sequences: A078643 A078644 A078645 this_sequence A078647 A078648 A078649
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Dec 13 2002
|
|
|
Search completed in 0.002 seconds
|
