This site is supported by donations to The OEIS Foundation.

 Annual appeal: Please make a donation to keep the OEIS running! Over 6000 articles have referenced us, often saying "we discovered this result with the help of the OEIS". Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A066733 Numbers such that the nonzero product of the digits of its square is also a square. 1
 1, 2, 3, 7, 12, 17, 21, 38, 88, 106, 107, 108, 109, 117, 122, 128, 129, 141, 146, 164, 168, 171, 173, 178, 191, 196, 204, 206, 207, 208, 209, 212, 221, 222, 236, 263, 276, 278, 288, 306, 342, 359, 364, 367, 372, 377, 394, 432, 463, 478, 479, 518, 537, 538 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Harry J. Smith, Table of n, a(n) for n = 1..1000 EXAMPLE 17 is in the sequence because the square of 17 is 289 and 2*8*9 = 144 = 12^2. MATHEMATICA Do[a = Apply[Times, IntegerDigits[n^2]]; If[ a != 0 && IntegerQ[a^(1/2)], Print[n]], {n, 1, 10^4} ] nzpQ[n_]:=Module[{prod=Times@@IntegerDigits[n^2]}, prod!=0 && IntegerQ[ Sqrt[ prod]]]; Select[Range[600], nzpQ] (* Harvey P. Dale, May 27 2012 *) PROG (PARI) ProdD(x)= { local(p=1); while (x>9 && p>0, p*=x%10; x\=10); return(p*x) } { n=0; for (m=1, 10^10, if (issquare(p=ProdD(m^2)) && p > 0, write("b066733.txt", n++, " ", m); if (n==1000, return)) ) } \\ Harry J. Smith, Mar 20 2010 CROSSREFS Cf. A067071. Sequence in context: A080140 A019568 A128458 * A049623 A228828 A061577 Adjacent sequences:  A066730 A066731 A066732 * A066734 A066735 A066736 KEYWORD nonn,base AUTHOR Robert G. Wilson v, Jan 15 2002 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.