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Search: id:A110921
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| A110921 |
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Numbers n with the property that if s denotes the sum of the digits of n, then s times s-reversed = n. |
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+0
2
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OFFSET
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1,2
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REFERENCES
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Tricky Number, Science Illustrated, Jan/Feb 2009, p. 80. [From Jonathan Vos Post (jvospost3(AT)gmail.com), Dec 20 2008]
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LINKS
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Masahiko Fujiwara, Title?.
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FORMULA
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k such that A007953(k)*A004086(A007953(k)) = k. [From Jonathan Vos Post (jvospost3(AT)gmail.com), Dec 20 2008]
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EXAMPLE
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Example: n = 1729: s = 1+7+2+9=19, 19*91=1729.
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PROGRAM
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#!/usr/bin/perl -w use strict; my $i; my $j; for $i ( 1e0 .. 1e6 ) { my $sum = 0; my $rev = 0; for $j ( 1 .. length ( $i ) ) { $sum += substr ( $i, $j - 1, 1 ); } $rev = reverse $sum; print "$i " if $sum * $rev == $i; }
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CROSSREFS
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Cf. A004086, A007953. [From Jonathan Vos Post (jvospost3(AT)gmail.com), Dec 20 2008]
Sequence in context: A016768 A059977 A116205 this_sequence A096302 A107914 A050634
Adjacent sequences: A110918 A110919 A110920 this_sequence A110922 A110923 A110924
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KEYWORD
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fini,full,nonn
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AUTHOR
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Michael Vang (michael.vang(AT)gmail.com), Sep 22 2005
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EXTENSIONS
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Edited by N. J. A. Sloane (njas(AT)research.att.com), Jan 15 2009, at the suggestion of Klaus Brockhaus
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