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A062936
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Numbers n such that n*R(n) is a palindrome, where R(n) (A004086) = digit reversal.
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2
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1, 2, 3, 11, 12, 21, 22, 101, 102, 111, 112, 121, 122, 201, 202, 211, 212, 221, 1001, 1002, 1011, 1012, 1021, 1022, 1101, 1102, 1111, 1112, 1121, 1201, 1202, 1211, 2001, 2002, 2011, 2012, 2021, 2101, 2102, 2111, 2201, 10001, 10002, 10011, 10012
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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LINKS
| Harry J. Smith, Table of n, a(n) for n=1,...,500
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FORMULA
| Includes integers not ending in 0 with sum of squares of digits < 10. - David W. Wilson (davidwwilson(AT)comcast.net), Jul 06, 2001.
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EXAMPLE
| 122*221 = 26962 hence 122 belongs to the sequence.
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MATHEMATICA
| Select[Range[100000], Reverse[IntegerDigits[ #*FromDigits[Reverse[IntegerDigits[ # ]]]]] == IntegerDigits[ #*FromDigits[Reverse[IntegerDigits[ # ]]]] &] [From Tanya Khovanova (tanyakh(AT)yahoo.com), Jun 17 2009]
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PROG
| (PARI) digitsIn(x)= { local(d); if (x==0, return(1)); d=1 + log(x)\log(10); if (10^d == x, d++, if (10^(d-1) > x, d--)); return(d) } Palin(x)= { local(y, d, e, f); if (x==0, return(1)); y=x; d=digitsIn(x); t=10^(d - 1); for (i=1, d\2, f=y-10*(y\10); y\=10; e=x\t; x-=t*e; t/=10; if (e!=f, return(0)) ); return(1) } Rev(x)= { local(d); r=0; while (x>0, d=x-10*(x\10); x\=10; r=r*10 + d); return(r) } { n=0; for (m=1, 10^9, if (Palin(m*Rev(m)), write("b062936.txt", n++, " ", m); if (n==500, break)) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Aug 13 2009]
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CROSSREFS
| Cf. A048344, A048343.
Sequence in context: A116029 A060812 A172409 * A136972 A135115 A107402
Adjacent sequences: A062933 A062934 A062935 * A062937 A062938 A062939
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KEYWORD
| nonn,base,easy
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Jul 05 2001
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EXTENSIONS
| Corrected and extended by Dean Hickerson (dean.hickerson(AT)yahoo.com) and Patrick De Geest, Jul 06, 2001
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