A226871 Triangle read by rows: row n gives the first q divisors d(1), d(2), ..., d(q) of A225110(n) such that Sum_{i = 1..q} 1/d(i) is an integer.
1, 1, 2, 3, 6, 1, 2, 3, 6, 1, 2, 4, 7, 14, 28, 1, 2, 3, 6, 1, 2, 3, 6, 1, 2, 3, 6, 1, 2, 3, 6, 1, 2, 3, 6, 1, 2, 3, 6, 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 30, 40, 60, 120, 1, 2, 3, 6, 1, 2, 3, 6, 1, 2, 3, 6, 1, 2, 3, 6, 1, 2, 3, 4, 5, 6, 9, 10, 12, 15, 18
Offset: 1
Examples
Row 3 = [1, 2, 3, 6] consists of the first 4 divisors of A225110(3) = 18; 1 + 1/2 + 1/3 + 1/6 = 2 is an integer.
Links
- Michel Lagneau, Rows n = 1..2223 of irregular triangle, flattened
Programs
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Maple
with(numtheory): print({1}):for n from 1 to 5000 do:x:=divisors(n):n1:=nops(x):s:=0:ii:=0:for q from 1 to n1 while(ii=0) do:s:=s+1/x[q]:if s=floor(s) and q>1 then ii:=1: print({seq(x[i],i=1..q)}) else fi:od:od:
Comments