OFFSET
1,1
COMMENTS
Multiples of terms in A053696.
Numbers of the form m*(b^n-1)/(b-1) for n > 2 and b > 1, m > 0.
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..10000
Wikipedia, Geometric progression.
EXAMPLE
7 is a term because 7 = 1 + 2 + 4.
13 is a term because 13 = 1 + 3 + 9.
14 is a term because 14 = 2 + 4 + 8.
15 is a term because 15 = 1 + 2 + 4 + 8.
PROG
(PARI) B(k, lim)={vector(logint(lim*(k-1)+1, k)-2, i, (k^(i+2) - 1)/(k-1))}
upto(lim=200)={my(v=concat(vector(sqrtint(lim)-1, k, B(k+1, lim)))); Set(concat(vector(#v, i, my(t=v[i]); t*[1..lim\t])))}
CROSSREFS
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Sep 19 2024
STATUS
approved