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

2,1

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.

Links

Harvey P. Dale, Table of n, a(n) for n = 2..1000

Example

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).

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 *)

Crossrefs

Cf. A136193, A032741 (row lengths).

Sequence in context: A248006 A197699 A005092 * A117892 A286098 A074372

Adjacent sequences: A136192 A136193 A136194 * A136196 A136197 A136198

Keyword

nonn,tabf

Author

Leroy Quet, Dec 20 2007

Extensions

More terms from Emeric Deutsch, Jan 05 2008

Status

approved