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A191486 Squares using only the prime digits (2,3,5,7). 6
25, 225, 7225, 27225, 55225, 235225, 2772225, 3553225, 23377225, 33235225, 57532225, 227557225, 252333225, 277722225, 337273225, 357777225, 523723225, 735223225, 777573225, 2523555225, 3325252225, 3377353225, 5232352225, 7333353225 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n) = 225 mod 1000 for n > 1. - Charles R Greathouse IV, May 14 2013

The sequence is infinite: it contains A030485 as an infinite proper subsequence which in turn contains all numbers of the form ((5*10^n-5)/3)^2 as a proper subsequence. - M. F. Hasler, Sep 16 2016

LINKS

Charles R Greathouse IV and Donovan Johnson, Table of n, a(n) for n = 1..1000 (first 155 terms from Charles R Greathouse IV)

FORMULA

a(n) = A275971(n)^2. - M. F. Hasler, Sep 16 2016

MAPLE

for b from 1 do convert(convert(b^2, base, 10), set) ; if % minus {2, 3, 5, 7} = {} then printf("%d, \n", b^2) ; end if; end do: # R. J. Mathar, Jun 03 2011

MATHEMATICA

w = Boole@! PrimeQ@ # & /@ RotateLeft@ Range[0, 9]; Select[Range[10^5]^2, Total@ Pick[DigitCount@ #, w, 1] == 0 &] (* Michael De Vlieger, Aug 15 2016 *)

PROG

(MAGMA) [n^2: n in [5..5*10^5] | Set(Intseq(n^2)) subset {2, 3, 5, 7}];  // Bruno Berselli, Jun 06 2011

(PARI) toprime(n, k)=n<<=2; sum(i=0, k-1, n>>=2; [2, 3, 5, 7][bitand(n, 3)+1]*10^i)

v=List([25]); for(k=0, 9, for(n=0, 4^k-1, t=1000*toprime(n, k)+225; if(issquare(t), listput(v, t)))); vecsort(Vec(v)) \\ Charles R Greathouse IV, May 14 2013

CROSSREFS

Cf. A077676, A030485.

Sequence in context: A058426 A189275 A048384 * A030485 A036509 A034981

Adjacent sequences:  A191483 A191484 A191485 * A191487 A191488 A191489

KEYWORD

nonn,base

AUTHOR

Giovanni Teofilatto, Jun 03 2011

STATUS

approved

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Last modified July 2 16:47 EDT 2020. Contains 335404 sequences. (Running on oeis4.)