A136195 Irregular array read by rows: row n contains the sums of each pair of consecutive positive divisors of n.
3, 4, 3, 6, 6, 3, 5, 9, 8, 3, 6, 12, 4, 12, 3, 7, 15, 12, 3, 5, 7, 10, 18, 14, 3, 9, 21, 4, 8, 20, 3, 6, 12, 24, 18, 3, 5, 9, 15, 27, 20, 3, 6, 9, 15, 30, 4, 10, 28, 3, 13, 33, 24, 3, 5, 7, 10, 14, 20, 36, 6, 30, 3, 15, 39, 4, 12, 36, 3, 6, 11, 21, 42, 30, 3, 5, 8, 11, 16, 25, 45
Offset: 2
Examples
The positive divisors of 20 are 1,2,4,5,10,20. 1+2=3. 2+4=6. 4+5=9. 5+10=15. 10+20=30. So row 20 is (3,6,9,15,30).
Links
- Harvey P. Dale, Table of n, a(n) for n = 2..1000
Programs
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Maple
with(numtheory): a:=proc(n) local dn: dn:=divisors(n): seq(dn[i]+dn[i+1],i= 1..nops(dn)-1) end proc: for n from 2 to 30 do a(n) end do; # Emeric Deutsch, Jan 05 2008
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Mathematica
Table[Total/@Partition[Divisors[n],2,1],{n,30}]//Flatten (* Harvey P. Dale, Mar 08 2022 *)
Extensions
More terms from Emeric Deutsch, Jan 05 2008
Comments