A159254 Numbers whose square ends with 49.

7, 43, 57, 93, 107, 143, 157, 193, 207, 243, 257, 293, 307, 343, 357, 393, 407, 443, 457, 493, 507, 543, 557, 593, 607, 643, 657, 693, 707, 743, 757, 793, 807, 843, 857, 893, 907, 943, 957, 993, 1007, 1043, 1057, 1093, 1107, 1143, 1157, 1193, 1207, 1243, 1257

Offset

1,1

Comments

First 7 terms = 7th row in A111445.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (1,1,-1).

Formula

a(1)=7, a(2)=43, a(n) = 50 + a(n-2).

From Colin Barker, Jul 04 2014: (Start)

a(n) = (11*(-1)^n + 50*n - 25)/2.

a(n) = a(n-1) + a(n-2) - a(n-3).

G.f.: x*(7*x^2+36*x+7) / ((x-1)^2*(x+1)). (End)

Mathematica

LinearRecurrence[{1, 1, -1}, {7, 43, 57}, 60] (* Harvey P. Dale, May 12 2025 *)

Prog

(PARI) select(n->n^2%100==49, vector(10^3, n, n)) \\ Colin Barker, Jul 04 2014

Crossrefs

A111445 Triangle read by rows: row n contains the first n numbers whose squares end in n^2.

Sequence in context: A376506 A376541 A045800 * A062336 A085704 A243459

Adjacent sequences: A159251 A159252 A159253 * A159255 A159256 A159257

Keyword

base,nonn,easy

Author

Zak Seidov, Apr 07 2009

Status

approved