A221310 Numbers m such that exactly four subsets of {m-1, m, m+1} sum up to a prime number.

1, 2, 3, 6, 30, 660, 810, 2130, 2550, 3330, 3390, 5850, 6270, 10530, 33180, 41610, 44130, 53550, 55440, 57330, 63840, 65100, 70380, 70980, 72270, 74100, 74760, 78780, 80670, 81930, 87540, 93240, 102300, 115470, 124770, 133980, 136950, 156420, 161460, 168450

Offset

1,2

Comments

A117499(a(n)) = 4;

(a(n)-1,a(n)+1) are twin prime pairs for n >= 4.

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..1000

Example

a(1) = 1: the required 4 subsets of {1-1,1,1+1} are: {2}, {0,2}, {1,2} and {0,1,2}.

Mathematica

Select[Range[170000], Count[Total/@Subsets[{#-1, #, #+1}], _?PrimeQ]==4&] (* Harvey P. Dale, Jul 30 2019 *)

Prog

(Haskell)
a221310 n = a221310_list !! (n-1)
a221310_list = map (+ 1) $ elemIndices 4 a117499_list

Crossrefs

Subsequence of A040040, apart from a(1)=1.

Sequence in context: A002234 A074005 A145499 * A082611 A033689 A018324

Adjacent sequences: A221307 A221308 A221309 * A221311 A221312 A221313

Keyword

nonn

Author

Reinhard Zumkeller, Jan 10 2013

Status

approved