A286901 - OEIS

%I #26 Feb 26 2018 20:53:13

%S 5,7,12,11,18,15,24,34,45,23,36,27,42,58,75,35,54,39,60,82,105,47,72,

%T 98,125,153,182,59,90,63,96,130,165,201,238,75,114,154,195,83,126,87,

%U 132,178,225,95,144,194,245,297,350,107,162,218,275,333,392,119,180,123

%N Sum of the numbers from prevprime(n) to n.

%C n is the lesser of twin primes (A001359) iff a(n+2) = A286900(n).

%H Chai Wah Wu, <a href="/A286901/b286901.txt">Table of n, a(n) for n = 3..10000</a>

%F a(n) = Sum_{i=prevprime(n)..n} i.

%p A286901:=n->add(i, i=prevprime(n)..n): seq(A286901(n), n=3..100);

%t Array[Total@ Range[NextPrime[#, -1], #] &, 60, 3] (* _Michael De Vlieger_, May 15 2017 *)

%o (Python)

%o from __future__ import division

%o from sympy import prevprime

%o def A286901(n):

%o     m = prevprime(n)

%o     return (m + n)*(n - m + 1)//2 # _Chai Wah Wu_, Feb 26 2018

%Y Cf. A001359, A286900 (sum of the numbers from n to nextprime(n)).

%K nonn,easy,look

%O 3,1

%A _Wesley Ivan Hurt_, May 15 2017

%E a(25) inserted by _Chai Wah Wu_, Feb 26 2018