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 A215952 Numbers n such that n^2 written in base 10 is of the form xyx where x is any string of digits and y is any single digit. 1
 1, 2, 3, 11, 22, 26, 173, 212, 263, 276, 16262, 27073, 193744, 208139, 311207, 2445865, 112791955, 142048458, 142837143, 153856154, 161933320, 164855165, 181838182, 200085674, 203701046, 213072687, 224870383, 225583910, 244765245, 252717253, 265704266 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS J. Brennen found the (prime) term 252717253. LINKS Jack Brennen, Table of n, a(n) for n = 1..66 Woodhodgson, Digit block repetition in prime squares, Yahoo! group primenumbers, Aug 28 2012. Woodhodgson, Jack Brennen, Maximilian Hasler, Digit block repetition in prime squares, digest of 7 messages in primenumbers Yahoo group, Aug 28 - Aug 30, 2012. EXAMPLE The squares of n=1,2,3 are < 10 and thus of the form xyx, where x is an empty string. a(4) = 11 since 11^2 = 121 = xyx  with  x=1 and y=2. a(7) = 173 since 173^2 = 29929 = xyx with x=29 and y=9. PROG (PARI) {t=1; m=3; for(n=1, 1e9, n>m & (m=sqrt((n=t*=10)^2*10)) & next; [.1, -1]*divrem(n^2, t)\1 || print1(n", "))} CROSSREFS Sequence in context: A002778 A028816 A316187 * A276375 A128921 A118595 Adjacent sequences:  A215949 A215950 A215951 * A215953 A215954 A215955 KEYWORD nonn,base AUTHOR M. F. Hasler, Aug 28 2012 EXTENSIONS a(17)-a(31) from Donovan Johnson, Aug 28 2012 STATUS approved

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Last modified December 4 08:57 EST 2021. Contains 349484 sequences. (Running on oeis4.)