

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
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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[200]^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



