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A081494
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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.
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3
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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; internal format)
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OFFSET
| 1,2
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FORMULA
| For n > 1, a(n) = A061761(n-1). - David Wasserman (wasserma(AT)spawar.navy.mil), Jun 03 2004
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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, a(4) = 13.
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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); # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 29 2009]
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CROSSREFS
| Cf. A081495, A081496, A081497.
Sequence in context: A078447 A066624 A061761 * A161909 A173168 A048462
Adjacent sequences: A081491 A081492 A081493 * A081495 A081496 A081497
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KEYWORD
| nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Mar 25 2003
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EXTENSIONS
| Corrected and extended by David Wasserman (wasserma(AT)spawar.navy.mil), Jun 03 2004
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