OFFSET
1,1
COMMENTS
REFERENCES
Popular Computing (Calabasas, CA), Problem 175: A Sum of a Different Kind, Vol. 5 (No. 50, May 1977), p. PC50-8.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..18
EXAMPLE
Since 1/3 + 1/5 + 1/7 + 1/11 + 1/13 + 1/17 + 1/19 + 1/23 < 1, the first eight odd primes are members. The ninth is not, because adding 1/29 pushes the sum over 1.
MATHEMATICA
a[n_] := a[n] = Block[{sm = Sum[1/(a[i]), {i, n - 1}]}, NextPrime[ Max[ a[n - 1], 1/(1 - sm)]]]; a[0] = 2; Array[a, 14]
CROSSREFS
KEYWORD
nonn
AUTHOR
Jonathan Sondow, May 11 2013
STATUS
approved