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 A081494 Start with Pascal's triangle; form a triangle by sliding down n steps from top on both sides and including the horizontal row, deleting the inner numbers; a(n) = sum of entries on perimeter of triangle. 4
 1, 3, 7, 13, 23, 41, 75, 141, 271, 529, 1043, 2069, 4119, 8217, 16411, 32797, 65567, 131105, 262179, 524325, 1048615, 2097193, 4194347, 8388653, 16777263, 33554481, 67108915, 134217781, 268435511, 536870969, 1073741883, 2147483709 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Table of n, a(n) for n=1..32. FORMULA For n > 1, a(n) = A061761(n-1). - David Wasserman, Jun 03 2004 EXAMPLE The triangle pertaining to n = 4 is obtained from the solid triangle 1 1 1 1 2 1 1 3 3 1 giving 1 1 1 1 1 1 3 3 1 and the sum of all the numbers is 13, so a(4) = 13. MAPLE restart:a:= proc(n) option remember; if n=0 then 1 else add((binomial (n, j)+2), j=0..n-1) fi end: seq (a(n), n=0..31); # Zerinvary Lajos, Mar 29 2009 CROSSREFS Cf. A081495, A081496, A081497. First differences of A290707. Sequence in context: A066624 A317783 A061761 * A161909 A281131 A173168 Adjacent sequences: A081491 A081492 A081493 * A081495 A081496 A081497 KEYWORD nonn AUTHOR Amarnath Murthy, Mar 25 2003 EXTENSIONS Corrected and extended by David Wasserman, Jun 03 2004 STATUS approved

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Last modified September 16 23:59 EDT 2024. Contains 375984 sequences. (Running on oeis4.)