OFFSET
0,5
COMMENTS
The integers are displayed as in A010371, where a 7 is depicted by 4 segments. The negative integers are depicted by using 1 segment more for the minus sign.
LINKS
FORMULA
EXAMPLE
a(7) = 14 since -111, -71, -41, -17, -14, -9, -6, 8, 12, 13, 15, 21, 31 and 51 are displayed by 7 segments.
__ __
__ | | | __ | | | __ |__| | __ | | | __ | |__|
| | | | | | | | | | |
(-111) (-71) (-41) (-17) (-14)
__ __ __ __ __ __ __
__ |__| __ |__ |__| | __| | __| | |__ __| |
__| |__| |__| | |__ | __| | __| |__ |
(-9) (-6) (8) (12) (13) (15) (21)
__ __
__| | |__ |
__| | __| |
(31) (51)
MATHEMATICA
P[x_]:=x^2+2x^4+3x^5+3x^6+x^7; c[n_]:=Coefficient[Sum[P[x]^k, {k, Max[1, Ceiling[n/7]], Floor[n/2]}], x, n]; b[n_]:=c[n]-c[n-6]; (* A331530 *)
a[n_]:=If[n!=7, b[n]+b[n-1], 14]; Array[a, 41, 0]
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Stefano Spezia, Dec 31 2021
STATUS
approved