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A007573 a(n) is the number of base numbers with 2n+1 digits in the asymmetric families of palindromic squares.
(Formerly M1319)
5
1, 2, 5, 6, 9, 10, 10, 15, 15, 16, 18, 24, 18, 26, 24, 30, 27, 33, 28, 40, 33, 40, 35, 48, 37, 50, 42, 53, 45, 58, 46, 64, 50, 64, 54, 72, 55, 73, 60, 78, 63, 82, 63, 88, 69, 88, 72, 95, 73, 98, 78, 102, 80, 106, 82, 112, 87, 111, 90, 120, 91, 122, 95, 126, 99, 130, 100, 135 (list; graph; refs; listen; history; text; internal format)
OFFSET
3,2
REFERENCES
M. Keith, Classification and enumeration of palindromic squares, J. Rec. Math., 22 (No. 2, 1990), 124-132.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
IBM Research Ponder This, Non-palindromic numbers with palindromic squares, October 2023 - Challenge.
M. Keith, Classification and enumeration of palindromic squares, J. Rec. Math., 22 (No. 2, 1990), 124-132. [Annotated scanned copy]. See foot of page 130.
G. J. Simmons, On palindromic squares of non-palindromic numbers, J. Rec. Math., 5 (No. 1, 1972), 11-19. [Annotated scanned copy]
EXAMPLE
a(3) = 1: The only base number of length 2*3 + 1 = 7 is 1109111 = A060087(1);
a(4) = 2 indicates the existence of two length 2*4 + 1 = 9 base numbers, 110091011 = A060087(2) and 111091111 = A060087(3).
PROG
(PARI) \\ see P. De Geest link.
CROSSREFS
Sequence in context: A269472 A351830 A244272 * A285663 A143909 A284507
KEYWORD
nonn,base
AUTHOR
EXTENSIONS
a(17)-a(31) from Sean A. Irvine, Jan 10 2018
Name and offset corrected by Hugo Pfoertner, Oct 04 2023
a(32)-a(70) from Hugo Pfoertner, Oct 07 2023
STATUS
approved

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Last modified February 27 11:46 EST 2024. Contains 370378 sequences. (Running on oeis4.)