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

Author

Leroy Quet, Dec 20 2007

Keywords

• nonn
• tabf

Comments

The first listed row is row 2. Row n contains d(n)-1 terms, where d(n) is the number of positive divisors of n.

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

Crossrefs

Cf. A136193, A032741 (row lengths).

Programs

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

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