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 A308003 A modified Sisyphus function: a(n) = concatenation of (number of even digits in n) (number of digits in n) (number of odd digits in n). 3
 110, 11, 110, 11, 110, 11, 110, 11, 110, 11, 121, 22, 121, 22, 121, 22, 121, 22, 121, 22, 220, 121, 220, 121, 220, 121, 220, 121, 220, 121, 121, 22, 121, 22, 121, 22, 121, 22, 121, 22, 220, 121, 220, 121, 220, 121, 220, 121, 220, 121, 121, 22, 121, 22, 121 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS If we start with n and repeatedly apply the map i -> a(i), we eventually reach 132 (see A073054). REFERENCES M. E. Coppenbarger, Iterations of a modified Sisyphus function, Fib. Q., 56 (No. 2, 2018), 130-141. LINKS N. J. A. Sloane, Table of n, a(n) for n = 0..28000 EXAMPLE 11 has 2 digits, both odd, so a(11)=22 (leading zeros are omitted). 12 has 2 digits, one even and one odd, so a(12)=121. Then a(121) = 132. MAPLE # Maple code based on R. J. Mathar's code for A171797: nevenDgs := proc(n) local a, d; a := 0 ; for d in convert(n, base, 10) do if type(d, 'even') then a :=a +1 ; end if; end do; a ; end proc: cat2 := proc(a, b) local ndigsb; ndigsb := max(ilog10(b)+1, 1) ; a*10^ndigsb+b ; end: catL := proc(L) local a, i; a := op(1, L) ; for i from 2 to nops(L) do a := cat2(a, op(i, L)) ; end do; a; end proc: A055642 := proc(n) max(1, ilog10(n)+1) ; end proc: A308003 := proc(n) local n1, n2 ; n1 := A055642(n) ; n2 := nevenDgs(n) ; catL([n2, n1, n1-n2]) ; end proc: seq(A308003(n), n=0..80) ; PROG (Python) def a(n): s = str(n) e = sum(1 for c in s if c in "02468") return int(str(e) + str(len(s)) + str(len(s)-e)) print([a(n) for n in range(55)]) # Michael S. Branicky, Mar 29 2022 CROSSREFS Cf. A073053 (Sisyphus), A171797, A171798, A171813, A055642, A196563, A196564, A308002. A073054 gives steps to reach 132. Sequence in context: A266301 A163597 A266606 * A288057 A288128 A281849 Adjacent sequences: A308000 A308001 A308002 * A308004 A308005 A308006 KEYWORD nonn,base,easy AUTHOR N. J. A. Sloane, May 12 2019 STATUS approved

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Last modified June 13 02:42 EDT 2024. Contains 373366 sequences. (Running on oeis4.)