A321350 Triangle read by rows: first row is 2; given row k, define the elements of row k+1 to be the (sorted) elements derived from row k by two recursion rules: (i.) if x is in row k, then (x+3)^2 is in row k+1; (ii.) if x^2 is in row k, then x is in row k+1.

2, 25, 5, 784, 28, 64, 619369, 8, 787, 961, 4489, 383621674384, 31, 67, 121, 619372, 624100, 929296, 20178064, 147165589059485451825769, 11, 790, 964, 1156, 4492, 4900, 15376, 383621674387, 383625390625, 389504554609, 863596631401, 407154387856489, 21657710603225344113280242498332241368243395984

Offset

1,1

Comments

A variant of A296142, a sequence inspired by problem A1 on the 2017 William Lowell Putnam Mathematical Competition.

Links

Table of n, a(n) for n=1..33.

Example

First few rows are
2;
25;
5, 784;
28, 64, 619369;
8, 787, 961, 4489, 383621674384;
31, 67, 121, 619372, 624100, 929296, 20178064, 147165589059485451825769;
11, 790, 964, 1156, 4492, 4900, 15376, 383621674387, 383625390625, 389504554609, 863596631401, 407154387856489, 21657710603225344113280242498332241368243395984;

Crossrefs

Cf. A296142, A321351.

Sequence in context: A045510 A226325 A065665 * A249634 A161575 A036502

Adjacent sequences: A321347 A321348 A321349 * A321351 A321352 A321353

Keyword

nonn,tabf

Author

Jeremy F. Alm, Nov 06 2018

Status

approved