A075703 a(n) = maximal m such that Sum_{k=n..m} prime(k) <= prime(n)*prime(m).

3, 6, 11, 16, 25, 28, 38, 43, 51, 64, 70, 83, 90, 95, 105, 117, 131, 134, 148, 158, 161, 174, 182, 196, 212, 225, 228, 235, 238, 248, 277, 287, 302, 305, 325, 332, 343, 355, 364, 380, 391, 394, 414, 419, 428, 433, 463, 486, 495, 498, 506, 519, 524, 544, 556

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..3000

Felice Russo, On a problem concerning the Smarandache friendly prime pairs.

Maple

Primes:= [seq(ithprime(i), i=1..1000)]:
S:= ListTools:-PartialSums(Primes):
f:= proc(n) local m, t;
    for m from n do if S[m] > S[n-1] + Primes[n]*Primes[m] then return m-1 fi od
end proc:
f(1):= 3:
map(f, [$1..100]); # Robert Israel, Aug 08 2019

Mathematica

f[n_] := Block[{k = n, s = 0, a = Prime[n]}, While[b = Prime[k]; s = s + b; a*b >= s, k++ ]; k--; k]; Table[ f[n], {n, 1, 55}]

Crossrefs

Cf. A074968.

Sequence in context: A087099 A181947 A366969 * A267583 A364198 A277023

Adjacent sequences: A075700 A075701 A075702 * A075704 A075705 A075706

Keyword

nonn,easy

Author

Roger L. Bagula, Oct 02 2002

Extensions

Edited by N. J. A. Sloane and Robert G. Wilson v, Oct 04 2002

Corrected by Robert Israel, Aug 08 2019

Status

approved