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 A250257 Least nonnegative integer whose decimal digits divide the plane into n regions. 2
 1, 0, 8, 48, 88, 488, 888, 4888, 8888, 48888, 88888, 488888, 888888, 4888888, 8888888, 48888888, 88888888, 488888888, 888888888, 4888888888, 8888888888, 48888888888, 88888888888, 488888888888, 888888888888, 4888888888888, 8888888888888, 48888888888888 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Equivalently, with offset 0, least nonnegative integer with n holes in its decimal digits. Leading zeros are not permitted. Identical to A249572 except that a(2) = 0, not 4. See also the comments in A249572. LINKS FORMULA a(n) = 10*a(n-2) + 8 for n >= 5. From Chai Wah Wu, Jul 12 2016: (Start) a(n) = a(n-1) + 10*a(n-2) - 10*a(n-3) for n > 5. G.f.: x*(-40*x^4 + 50*x^3 - 2*x^2 - x + 1)/((x - 1)*(10*x^2 - 1)). (End) EXAMPLE The integer 48, whose decimal digits have 3 holes, divides the plane into 4 regions. No smaller nonnegative integer does this, so a(4) = 48. MATHEMATICA Join[{1, 0, 8}, RecurrenceTable[{a==48, a==88, a[n]==10 a[n-2] + 8}, a, {n, 20}]] (* Vincenzo Librandi, Nov 16 2014 *) PROG (MAGMA) I:=[1, 0, 8, 48, 88]; [n le 5 select I[n] else 10*Self(n-2)+8: n in [1..30]]; // Vincenzo Librandi, Nov 15 2014 CROSSREFS Cf. A249572, A250256, A250258, A001743, A001744, A001745, A001746, A002282. Sequence in context: A165037 A121028 A139279 * A067239 A152750 A121355 Adjacent sequences:  A250254 A250255 A250256 * A250258 A250259 A250260 KEYWORD nonn,base,easy AUTHOR Rick L. Shepherd, Nov 15 2014 STATUS approved

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Last modified July 4 08:33 EDT 2020. Contains 335444 sequences. (Running on oeis4.)