A376298 Numbers which are the sum of at least three successive terms of a geometric progression.
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
Keywords
Examples
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.
Links
- Andrew Howroyd, Table of n, a(n) for n = 1..10000
- Wikipedia, Geometric progression.
Programs
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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])))}
Comments