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A110621 Shadow of Pi. 1
1, 4, 18, 33, 42, 44, 50, 55, 90, 98, 195, 288, 311, 395, 457, 521, 859, 891, 898, 1848, 1876, 2717, 3688, 3757, 3796, 4733, 5243, 5301, 5321, 6295, 6389, 6434, 6526, 6556, 6634, 6650, 6690, 7318, 7938, 8027, 9013, 9293, 9327, 9409, 9462, 9883, 10053 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

First differences are Pi's shadow. Never twice the same integer in sequence or first differences.

LINKS

Table of n, a(n) for n=1..47.

EXAMPLE

The first line hereunder is the sequence, the second line are the first differences:

1.4..18..33.42.44.50.55..90.98..195..288..311...

.3.14..15..9..2..6..5..35..8..97...93...23 <-- Pi shadow

(Pi=3.141592653589793238462643383279502884197169399...)

MATHEMATICA

a[1] = 1; a[n_] := a[n] = Block[{c = RealDigits[Pi, 10, 300][[1]], k = 1, t = Table[a[i], {i, n - 1}]}, d = Drop[t, 1] - Drop[t, -1]; b = Drop[c, Length[ Flatten[ IntegerDigits /@ d]]]; e = Union[ Join[t, d]]; While[f = FromDigits[ Take[b, k]]; Position[e, f] != {} || b[[k + 1]] == 0, k++ ]; f + a[n - 1]]; Table[ a[n], {n, 47}] (* Robert G. Wilson v *)

CROSSREFS

Cf. A000796.

Sequence in context: A095823 A092116 A083969 * A124978 A031081 A009956

Adjacent sequences:  A110618 A110619 A110620 * A110622 A110623 A110624

KEYWORD

easy,nonn,base

AUTHOR

Eric Angelini and Alexandre Wajnberg, Sep 14 2005

EXTENSIONS

More terms from Robert G. Wilson v, Oct 10 2005

STATUS

approved

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Last modified December 7 20:44 EST 2019. Contains 329849 sequences. (Running on oeis4.)