A201156 - OEIS

%I #8 Mar 31 2012 10:24:06

%S 1,3,10,11,56,57,400,401,402,403,4434,4435,57656,57657,57658,57659,

%T 980204,980205,18623896,18623897,18623898,18623899,428349678,

%U 428349679,428349680,428349681,428349682,428349683,12422140808,12422140809,385086365080,385086365081

%N Row sums of triangle A201146.

%C a(n) = a(n-1) + 1 if and only if n is a composite number.

%H Arkadiusz Wesolowski, <a href="/A201156/b201156.txt">Table of n, a(n) for n = 1..502</a>

%t Table[Sum[Product[Prime[i], {i, PrimePi[n]}]/Product[Prime[i], {i, PrimePi[k]}], {k, n}], {n, 32}]

%Y Cf. A201146.

%K nonn

%O 1,2

%A _Arkadiusz Wesolowski_, Nov 27 2011