A126597 Triangle read by rows: Start with the row 1,2. To get the next row, do the following: if the sum of two adjacent terms is odd then insert this sum in between them, otherwise insert the absolute value of their difference; repeat the procedure.

1, 2, 1, 3, 2, 1, 2, 3, 5, 2, 1, 3, 2, 5, 3, 2, 5, 7, 2, 1, 2, 3, 5, 2, 7, 5, 2, 3, 5, 2, 7, 5, 2, 7, 9, 2, 1, 3, 2, 5, 3, 2, 5, 7, 2, 9, 7, 2, 5, 7, 2, 5, 3, 2, 5, 7, 2, 9, 7, 2, 5, 7, 2, 9, 7, 2, 9, 11, 2, 1, 2, 3, 5, 2, 7, 5, 2, 3, 5, 2, 7, 5, 2, 7, 9, 2, 11, 9, 2, 7, 9, 2, 7, 5, 2, 7, 9, 2, 7, 5, 2, 3, 5, 2, 7

Offset

1,2

Links

Table of n, a(n) for n=1..105.

Formula

{s(i),s(i+1)} => {s(i),s(i)+s(i+1), s(i+1)}, if s(i)+s(i+1) is odd, otherwise {s(i),s(i+1)} => {s(i), abs(s(i)-s(i+1)), s(i+1)}.

Example

Triangle begins:
1,2
1,3,2
1,2,3,5,2
1,3,2,5,3,2,5,7,2
1,2,3,5,2,7,5,2,3,5,2,7,5,2,7,9,2
1,3,2,5,3,2,5,7,2,9,7,2,5,7,2,5,3,2,5,7,2,9,7,2,5,7,2,9,7,2,9,11,2

Mathematica

s={1, 2}; Do[t=s; ti=1; Do[If[OddQ[su=s[[i]]+s[[i+1]]], t=Insert[t, su, i+ti], t=Insert[t, Abs[s[[i]]-s[[i+1]]], i+ti]]; ti++, {i, Length[s]-1}]; Print[t]; s=t, {8}]

Crossrefs

Sequence in context: A285731 A114905 A200651 * A261867 A076081 A304089

Adjacent sequences: A126594 A126595 A126596 * A126598 A126599 A126600

Keyword

nonn,tabf

Author

Zak Seidov, Mar 13 2007

Status

approved