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A255342 Numbers n such that there are exactly two 1's in their factorial base representation (A007623). 6
3, 7, 8, 11, 15, 21, 25, 26, 29, 30, 34, 37, 38, 41, 43, 44, 47, 51, 55, 56, 59, 63, 69, 75, 79, 80, 83, 87, 93, 99, 103, 104, 107, 111, 117, 121, 122, 125, 126, 130, 133, 134, 137, 139, 140, 143, 144, 148, 156, 160, 162, 166, 169, 170, 173, 174, 178, 181, 182, 185, 187, 188, 191, 193, 194, 197, 198, 202 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..13132

EXAMPLE

The factorial base representation (A007623) of 3 is "11", which contains exactly two 1's, thus 3 is included in the sequence.

The f.b.r. of 7 is "101", with exactly two 1's, thus 7 is included in the sequence.

The f.b.r. of 21 is "311", with exactly two 1's, thus 21 is included in the sequence.

MATHEMATICA

factBaseIntDs[n_] := Module[{m, i, len, dList, currDigit}, i = 1; While[n > i!, i++]; m = n; len = i; dList = Table[0, {len}]; Do[currDigit = 0; While[m >= j!, m = m - j!; currDigit++]; dList[[len - j + 1]] = currDigit, {j, i, 1, -1}]; If[dList[[1]] == 0, dList = Drop[dList, 1]]; dList]; s = Table[FromDigits[factBaseIntDs[n]], {n, 240}]; Flatten@ Position[s, x_ /; DigitCount[x][[1]] == 2](* Michael De Vlieger, Apr 27 2015, after Alonso del Arte at A007623 *)

PROG

(Scheme, with Antti Karttunen's IntSeq-library)

(define A255342 (MATCHING-POS 1 0 (lambda (n) (= 2 (A257511 n)))))

CROSSREFS

Cf. A007623, A257511, A255411, A255341, A255343.

Subsequence of A256450.

Subsequence: A038507 (apart from its initial 2 terms).

Sequence in context: A069122 A278519 A007970 * A134258 A028972 A153030

Adjacent sequences:  A255339 A255340 A255341 * A255343 A255344 A255345

KEYWORD

nonn,base

AUTHOR

Antti Karttunen, Apr 27 2015

STATUS

approved

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Last modified November 17 04:01 EST 2018. Contains 317275 sequences. (Running on oeis4.)