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A323645
a(n) is the number of visible faces in the perspective view of the stepped pyramid with n levels described in A245092.
1
3, 6, 12, 17, 21, 28, 32, 39, 46, 56, 60, 69, 73, 81, 92, 103, 107, 118, 122
OFFSET
1,1
COMMENTS
The shape of the n-th level of the pyramid allows us to know if n is prime (see the Formula section).
For more sequences that we can find in the pyramid see A262626.
FORMULA
a(n) = a(n-1) + 4 iff n is a prime > 3 (A215848).
a(n) = A325300(n) - 3. - Omar E. Pol, Apr 17 2019
KEYWORD
nonn,more
AUTHOR
Omar E. Pol, Mar 20 2019
EXTENSIONS
a(18)-a(19) from Omar E. Pol, Apr 18 2019
STATUS
approved