A077487 Squares which leave a square at every step if most significant digit and least significant digit are deleted until a one-digit or two-digit square is obtained.

1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 144, 196, 400, 441, 841, 900, 1369, 3364, 4096, 5041, 8649, 10000, 10816, 11449, 20164, 38416, 40000, 61009, 64009, 90000, 1000000, 1004004, 3013696, 3108169, 4000000, 4004001, 9000000, 100000000

Offset

1,2

Comments

Sequence is infinite with nontrivial terms (10^(2k+1)+2)^2 and (2*10^(2k+1)+1)^2. - Ray Chandler, Aug 03 2003

Links

Table of n, a(n) for n=1..38.

Example

38416 is a member as 38416, 841 and 4 all are squares.

Prog

(PARI) l=listcreate(1000); for(n=0, 9, listput(l, n^2)); for(k=3, 50, for(d1=1, 9, for(n=1, length(l), for(d2=0, 9, t1=l[n]; if(t1<10^(k-2), c=d1*10^(k-1) + t1*10 + d2; if(issquare(c), listput(l, c); ); ); ); ); ); ); l

Crossrefs

Cf. A077485, A077486.

Sequence in context: A352618 A030476 A077355 * A179334 A068867 A068864

Adjacent sequences: A077484 A077485 A077486 * A077488 A077489 A077490

Keyword

base,nonn

Author

Amarnath Murthy, Nov 07 2002

Extensions

Corrected and extended by Ray Chandler, Aug 03 2003

Status

approved