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 A242097 Sp = reversal of some square s where s = x^2 for x = 1,2,.. (ignoring leading zeros). Sp is in the sequence if it is semiprime. 1
 4, 9, 94, 46, 121, 961, 982, 4, 526, 9, 169, 6511, 5221, 9481, 1042, 6313, 4633, 1843, 1273, 94, 1405, 9235, 46, 9886, 6937, 4069, 10201, 61801, 94411, 18811, 121, 44521, 96721, 52231, 65431, 42931, 67351, 52651, 92161, 48361, 961, 16171, 98671, 65971, 96781 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS All the terms in sequence are semiprimes (product of two primes) which are reversal of some square, ignoring leading zeros. LINKS K. D. Bajpai, Table of n, a(n) for n = 1..360 EXAMPLE a(3) = 94 = 2 * 47 which is semiprime. Reversing the digits gives 49 = 7^2. a(4) = 46 = 2 * 23 which is semiprime. Reversing the digits gives 64 = 8^2. MAPLE with(StringTools): with(numtheory): A242097:= proc() local r; r:= parse(Reverse(convert(x^2, string))); if bigomega(r)=2 then  RETURN (r); fi; end: seq(A242097 (), x=1..500); MATHEMATICA Select[IntegerReverse[Range^2], PrimeOmega[#]==2&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, May 27 2018 *) CROSSREFS Cf. A001358, A115710, A115711. Sequence in context: A077530 A115551 A227419 * A220972 A247009 A245241 Adjacent sequences:  A242094 A242095 A242096 * A242098 A242099 A242100 KEYWORD nonn,base,less AUTHOR K. D. Bajpai, May 04 2014 STATUS approved

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Last modified January 27 08:31 EST 2020. Contains 331293 sequences. (Running on oeis4.)