A103622 Smallest arithmetic mean of n distinct primes.

2, 4, 4, 7, 6, 11, 10, 13, 12, 17, 16, 21, 20, 24, 24, 29, 26, 32, 32, 36, 36, 41, 38, 45, 44, 49, 48, 53, 52, 58, 58, 63, 62, 68, 66, 72, 70, 77, 76, 83, 80, 87, 86, 92, 90, 97, 96, 102, 100, 108, 106, 113, 110, 118, 116, 123, 122, 129, 126, 133, 132, 139, 138, 145, 142

Offset

1,1

Comments

Often a(2n+1) = a(2n) - 1. - Robert G. Wilson v, Jan 19 2007

Links

Table of n, a(n) for n=1..65.

Example

a(1)=2 because (2)/1=2,
a(2)=4 because (3+5)/2=4,
a(3)=4 because (2+3+7)/3=4,
a(4)=7 because (3+5+7+13)/4=7,
a(5)=6 because (2+3+5+7+13)/5=6,
a(6)=11 because (3+5+7+11+17+23)/6=11,
a(7)=10 because (2+3+5+7+11+13+29)/7=10,
a(8)=13 because (3+5+7+11+13+17+19+29)/8=13,
a(9)=12 because (2+3+5+7+11+13+17+19+31)/9=12,
a(10)=17 because (3+5+7+11+13+17+19+23+29+43)/10=17, etc.

Mathematica

f[n_] := Block[{k = 1, lst = Prime@ Range[ If[ OddQ@ n, 1, 2], n + 3]}, While[ Mod[Plus @@ Flatten@Subsets[lst, {n}, {k}], n] != 0, k++ ]; (Plus @@ Flatten@ Subsets[lst, {n}, {k}])/n]; Array[f, 65] (* Robert G. Wilson v, Jan 19 2007 *)

Crossrefs

Cf. A072701.

Sequence in context: A082515 A062855 A274593 * A328853 A105774 A130805

Adjacent sequences: A103619 A103620 A103621 * A103623 A103624 A103625

Keyword

easy,nonn

Author

Giovanni Teofilatto, Mar 25 2005

Extensions

Edited, corrected and extended by Robert G. Wilson v, Jan 19 2007

Status

approved