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

Author

Reinhard Zumkeller, Jan 10 2013

Keywords

• nonn

Comments

A117499(a(n)) = 4;

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

Examples

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

Links

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

Crossrefs

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

Programs

Haskell

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

Mathematica

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