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A216261 Smallest number needing exactly n segments on calculator display. 2
1, 7, 4, 2, 0, 8, 10, 18, 22, 20, 28, 68, 88, 108, 188, 200, 208, 288, 688, 888, 1088, 1888, 2008, 2088, 2888, 6888, 8888, 10888, 18888, 20088, 20888, 28888, 68888, 88888, 108888, 188888, 200888, 208888, 288888, 688888, 888888, 1088888, 1888888, 2008888, 2088888, 2888888 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

COMMENTS

A006942(a(n)) = n and A006942(m) <> n for m < a(n).

LINKS

Table of n, a(n) for n=2..47.

FORMULA

a(n+7) = 10*a(n) + 8 for n > 10. This can be deduced from a(n) = min{10*a(n-A006942(r))+r, r=0..9} via strong induction.- David Radcliffe, Jan 29 2016

G.f.: (x^2 +6*x^3 -3*x^4 -2*x^5 -2*x^6 +8*x^7 +2*x^8 -2*x^9 -56*x^10 +28*x^11 +28*x^12 +60*x^13 -60*x^14 -28*x^17 +28*x^18)/((1-x)*(1-10*x^7)). - David Radcliffe, Jan 29 2016

MATHEMATICA

Drop[#, 2] &@ CoefficientList[Series[(x^2 + 6 x^3 - 3 x^4 - 2 x^5 - 2 x^6 + 8 x^7 + 2 x^8 - 2 x^9 - 56 x^10 + 28 x^11 + 28 x^12 + 60 x^13 - 60 x^14 - 28 x^17 + 28 x^18)/((1 - x) (1 - 10 x^7)), {x, 0, 50}], x] (* Michael De Vlieger, Jan 29 2016 *)

PROG

(Haskell)

import Data.Maybe (fromJust)

import Data.List (elemIndex)

a216261 = fromJust . (`elemIndex` a006942_list)

-- Reinhard Zumkeller, Mar 15 2013

(PARI) Vec((x^2 +6*x^3 -3*x^4 -2*x^5 -2*x^6 +8*x^7 +2*x^8 -2*x^9 -56*x^10 +28*x^11 +28*x^12 +60*x^13 -60*x^14 -28*x^17 +28*x^18)/((1-x)*(1-10*x^7)) + O(x^50)) \\ Michel Marcus, Jan 29 2016

CROSSREFS

Sequence in context: A187056 A103240 A155531 * A188628 A021578 A273093

Adjacent sequences:  A216258 A216259 A216260 * A216262 A216263 A216264

KEYWORD

nonn,base

AUTHOR

Reinhard Zumkeller, Mar 15 2013

STATUS

approved

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Last modified June 16 10:03 EDT 2019. Contains 324152 sequences. (Running on oeis4.)