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 A182452 Numbers for which the sum of reciprocals of square of digits is an integer. 0
 1, 11, 111, 1111, 2222, 11111, 12222, 21222, 22122, 22212, 22221, 111111, 112222, 121222, 122122, 122212, 122221, 211222, 212122, 212212, 212221, 221122, 221212, 221221, 222112, 222121, 222211, 222336, 222363, 222633, 223236, 223263, 223326, 223362, 223623 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE 223623 is in the sequence because 1/2^2 + 1/2^2 + 1/3^2 + 1/6^2 + 1/2^2 + 1/3^2 = 1 is integer. MAPLE T:=array(1..10):for n from 1 to 10^7 do:T:=convert(n, base, 10):n1:=nops(T): s:=0:j:=0:for k from 1 to n1 do:if T[k]<>0 then s:=s+evalf(1/T[k]^2):else j:=1:fi: od: if j=0 and s=floor(s) then printf(`%d, `, n):else fi:od: MATHEMATICA f[ n_ ] := 1/n^2; a[ n_ ] := Apply[ Plus, Map[ f, IntegerDigits[ n ] ] ] ; Select[ Range[ 1000 ], FreeQ[ IntegerDigits[ # ], 0 ] && IntegerQ[ a [ # ] ] & ] CROSSREFS Cf. A034708. Sequence in context: A334131 A077488 A039988 * A283006 A283257 A284088 Adjacent sequences:  A182449 A182450 A182451 * A182453 A182454 A182455 KEYWORD nonn,base AUTHOR Michel Lagneau, Apr 29 2012 STATUS approved

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Last modified December 7 02:57 EST 2021. Contains 349567 sequences. (Running on oeis4.)