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Search: id:A070253
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| A070253 |
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Numbers n such that n^2 - 1 is a palindrome. |
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+0
2
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| 1, 2, 3, 10, 18, 24, 65, 76, 100, 192, 205, 1000, 1748, 1908, 2366, 2967, 5732, 10000, 18992, 20565, 100000, 174602, 174748, 179318, 243064, 293787, 552102, 1000000, 1868288, 2967033, 9200157, 10000000, 22765896, 31552660, 93809717, 100000000
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Every palindrome of the form n^2-1 is of the form m(m+2) (easy to prove by substituting n with m+1). In fact this is equal to A028503 + 1. - Patrick De Geest, May 09, 2002.
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LINKS
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P. De Geest, Palindromic quasipronic numbers of the form n(n+2)
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MATHEMATICA
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Do[ If[ a = IntegerDigits[n^2 - 1]; a == Reverse[a], Print[n]], {n, 1, 10^8/4}]
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PROGRAM
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(PARI) intreverse(n)=local(d, rev); rev=0; while(n>0, d=divrem(n, 10); n=d[1]; rev=10*rev+d[2]); rev for(n=1, 100000000, q=n*n-1; if(q==intreverse(q), print1(n, ", ")))
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CROSSREFS
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Cf. A027719, A027720, A070254. Equals A028503 + 1.
Sequence in context: A060744 A143609 A066915 this_sequence A147673 A057507 A163467
Adjacent sequences: A070250 A070251 A070252 this_sequence A070254 A070255 A070256
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KEYWORD
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base,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), May 06 2002
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EXTENSIONS
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Edited by Jason Earls (zevi_35711(AT)yahoo.com), Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) and Robert G. Wilson v (rgwv(AT)rgwv.com), May 08 2002
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