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 A210652 Numbers whose waterfall sequence ends in 0,0,0,.... 1
 10, 15, 20, 25, 30, 35, 40, 45, 50, 51, 52, 53, 54, 55, 56, 57, 58, 60, 65, 69, 70, 75, 78, 80, 85, 87, 90, 95, 96, 98, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 115, 120, 125, 130, 135, 140, 145, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 165, 169, 170, 175, 178, 180, 185, 187, 190, 196, 200, 201, 202, 203 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The "waterfall" sequence S for a given starting value S(1) > 9 is defined as S(n) = d(n)*d(n-1) (n > 1), where d(n) is the n-th digit of the sequence. When S(1) has a digit 0 or 5, then S is likely to end up in repeating zeros. A210653 lists counterexamples, and A210614 is the subsequence of terms having no digit 0 or 5. LINKS E. Angelini, Waterfalls (of multiplications), Mar 27 2012 E. Angelini, Waterfalls (of multiplications) [Cached copy, with permission] PROG (PARI) is_A210652(n, L=2e3)={ my(S=eval(Vec(Str(n)))); for(i=1, L, (S=concat(vecextract(S, "^1"), eval(Vec(Str(n=S[1]*S[2]))))) | return(1))} \\ The optional 2nd parameter L is the limit prior to which the remaining digits must be all zero. The result may be wrong if L is not large enough, but large values of L yield slow computations for values NOT in this sequence. for(n=10, 999, is_A210652(n) & print1(n", ")) CROSSREFS Cf. A210653. Sequence in context: A232501 A138593 A004259 * A284804 A006623 A035166 Adjacent sequences:  A210649 A210650 A210651 * A210653 A210654 A210655 KEYWORD nonn,base AUTHOR M. F. Hasler, Mar 27 2012 STATUS approved

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Last modified December 1 01:37 EST 2021. Contains 349426 sequences. (Running on oeis4.)