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- ; Project Euler Problem 2
- ; Solution by nathan dotz - nathan (period) dotz (at sign) gmail (period) com
- ;
- ; Each new term in the Fibonacci sequence is generated by adding
- ; the previous two terms. By starting with 1 and 2, the first
- ; 10 terms will be:
- ; 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
- ;
- ; Find the sum of all the even-valued terms in the sequence
- ; which do not exceed four million.
- ;
- (defun fib (n)
- (defun fib-worker (n stack)
- (if (<= n (car stack))
- (cdr stack)
- (fib-worker n (cons (+ (first stack) (second stack)) stack))))
- (fib-worker n '(1 1))
- )
- (defun even-small-fib (small-fib)
- (remove-if-not 'evenp small-fib)
- )
- (princ (apply '+ (even-small-fib (fib 4000000)) ) )
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