login
A376298
Numbers which are the sum of at least three successive terms of a geometric progression.
2
7, 13, 14, 15, 21, 26, 28, 30, 31, 35, 39, 40, 42, 43, 45, 49, 52, 56, 57, 60, 62, 63, 65, 70, 73, 75, 77, 78, 80, 84, 85, 86, 90, 91, 93, 98, 104, 105, 111, 112, 114, 117, 119, 120, 121, 124, 126, 127, 129, 130, 133, 135, 140, 143, 146, 147, 150, 154, 155, 156, 157
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
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